I agree with you regarding the pinky for backspace. I saw a study somewhere that showed most people hit the normal backspace key with their ring finger, presumably because it's stronger. Of course, it's also longer, so isn't much harder to reach the backspace key with. But it still requires more hand movement for me. But yes, for hitting backspace multiple times (which I generally do as well), I find it preferable to not use the pinky.

I have the caps lock key mapped a virtual modifier in Karabiner on my Mac, so I don't have to mess with remapping Alt.  I have delete set to the colemak 'y'/qwerty 'o' key with that virtual modifier. Other keys on that modifier are mostly text navigation keys (arrow keys, etc).

I'm a fan of putting the less common punctuation as modified keys, as suggested. I have another virtual modifier for that (on the tab key). The problem there is that it's harder to use my left hand for either of those modifiers (on the caps lock or tab keys) with the modified key while maintaining the flow of typing, so that's a limiting factor. You can also look into "SpaceFN", where you use the spacebar as a modifier (i.e. a space typed by itself is a space, but when held down is a modifier). It's a little tricky to make it work in a way that does not mess with your typing flow, too, but I managed to get pretty good at it. However, I eventually stopped using it because I still occasionally got typos that way.

I also switch the parentheses with the '<' and '>', since I and most people use parenteses far more commonly (unless you are an HTML/XML programmer, perhaps), but modified home keys for parenteses should be equivalent, if not better since they are on the home row.

In short, I give you the thumbs up on experimenting with remapping! Even if I agree it's kind of a virus. :-P

Edit: also, for people who say Colemak is not really any better than qwerty, they are probably talking about typing speed (rather than comfort), which many people never really exceed by much by switching to alternative layouts. It certainly IS possible to type very fast with qwerty, but of course it requires a lot of hand/finger movement. I think the limiting factor in typing very fast is generally not hand movement but is more neurological, in how closely you can coordinate your fingers to hit the keys in sequence without making typos. I think it's much quicker to get up to reasonable speed on optimized layouts. But champion typers are often qwerty typists for the obvious reason that there are a lot more of them. Switching layouts involves effort in the beginning, and only pays off in the long term, so people who can type fast on qwerty and don't have significant hand pain/fatigue may not feel it's worth the switch.

Thanks for the quick replies. The backspace key is just one of those things that makes perfect sense in one context and is a lot of nonsense in another; visually it makes perfect sense, but from a tactile point of view―i.e. when touch typing―it could hardly be in a more inconvenient place. In this case there's no reason at all, IMHO, not to allocate a more central position. Nice to hear there are others out there who've thought of the same! With the European physical keyboard design I've got slightly more keys to play around with than with the US design, but I've assigned the letters Æ, Ø, & Å of my native Norwegian to three of the symbol keys, and in the end I've pretty much only got left two symbol-only keys―apostrophe & hyphen―within easy reach. There are a few more; one I use for caps-lock and the others I use as dead keys. At the moment, I'm only using the right hand homerow keys with the CAPS LOCK-turned-modifier key, which makes it quite easy to use.

I had a look at DreymaR's Big Bag. I can see you're playing in a whole different league. Wow! I don't have a desktop computer and am doing almost all of my typing on a Samsung tablet, which, I guess, makes my options a bit more limited. Like you I like to be able to type a whole range of characters and diacritics not included in your ordinary keyboard layout, so I've also done a lot of re-mapping so as to be able to type most of these with the help of Alt and AltGr (that, incidentally, is why I've only got the right hand side of the home row available for ordinary symbols). I found your Colemak[eD] Norwegian layout quite interesting, but don't think it will work for me to implement it, since the Norwegian qwerty Ø and Æ keys in my foldable keyboard have been horribly (and unforgivably) compressed so as to make them fit. I may have a go and move Z, X, C, & B one key to the left, though. Never thought of that one!

You know what, I came to exactly the same conclusion too, although my solution is different to yours.

I started off using the DreymaR's "Extend" layer mappings, with CapsLock as the Extend key, and Caps-O as the backsace key. This is certainly a massive improvement over the default backspace position, but I was never entirely happy with using both pinkies all the time for such a common (in my case anyway) action.  After some experimentation I eventually settled on a new configuration which I have since found to be very satisfying:

My Extend key is now Left ALT, and is pressed with the left thumb. I find that Left ALT works better than CapsLock as a modifier key. Backspace is mapped to  Extend-H (using Mod-DH as my layout).  This means backspace is done with left thumb plus right index finger. Because H (in my layout) is almost directly under the index finger home position, it is extremely fast and comfortable to type, and because it's on a strong finger, you can make lots of errors safely without tiring out pinkies!

In any case Extend layer is a wonderful thing I encourage folks to experiment with it.

I wonder if that was me, I have limited (actually non-existent) need for typing accented characters, so I use my right ALT to create as a layer with common symbols, brackets etc. Thumb keys modifiers on Alt keys are way to go!

I only use the on-screen keyboard for very short pieces of writing. For anything more than a sentence or so, I use an external keyboard (Microsoft Universal Foldable Keyboard). I've had a look at your Big Bag post, and as a consequence my keyboard's all a good old mess again. :-) (Before that I was already inching my way towards 50 wpm in the (almost) standard Colemak layout...) The first thing I did was to move the bottom left row one key to the left, as indicated in the "Cawmak" layout. In a way that was easier than swopping letters around, in that the same fingers were hitting the same letters, but it did feel strange at first to change the angle of the hand! I had to do a lot of "tv-sc-rx-az" sequences and comparisons with the right hand before I could really believe it to be better than the old way. Eventually it started to sink in, though, at which point it did indeed start to feel like a "no-brainer". Then, while I was at it, I couldn't restrain myself from changing the positionings of b, g, & d, as well, as per the Cawmak layout.
That, as it turned out wasn't actually too much of a shock to the system. It seems to be true that making the changes small steps at a time is a good way to make the transition to a new layout.
Anyhow, I'm still quite happy with my own "improvement" of allocating backspace to the index finger. But now that I'm already in the mood for re-mapping, I've been toying with the idea of really going all the way and re-mapping it to qwerty-H instead. Then re-map J back to qwerty-Y and H to qwerty-N (again, as suggested in the Cawmak layout). Apart from the backspace, my only original re-mapping would be K to qwerty-O and Y to qwerty-P. (As I've also assigned Æ, Ø, and Å to the right pinkie, I decided on moving the, in Norwegian, relatively infrequent Y to this finger, so as to not overload it when typing in Norwegian.)
I'd be interested to hear any advice/suggestions/opinions anyone might have on these weighty matters ...

Hmm... I'm trying to include some images. Does anyone have some good advice as to how I might accomplish that? I read the help page but couldn't quite figure it out...

Phew! After much re-mapping back and forth, I think/hope I've now settled on a final layout. My typing is still not as certain and as quick as it was before I started modifying the standard Colemak design along the lines of DreymaR's "ColemakCAW" layout, but after a set-back of a couple of weeks I'm getting close again—and I'm just now starting to appreciate the ergonomic advantages as well. Changing to that layout opened up the possibility of getting the Backspace key down to the homerow, to what I consider one of the most desirable keys for that function—qwerty-H. So, to cut a long story short, after a few more days of dithering and a few more re-mappings later, I eventually went ahead and did just that. Below is what I've come up with. First with the standard Colemak layout, then with DreymaR's ColemakCAW modified layout.

1. Standard Colemak layout:  Backspace re-mapped to qwerty-H. [J] has been re-mapped to qwerty-P.

2. DreymaR's ColemakCAW (=CAWmak) layout:  Backspace re-mapped to qwerty-H. [K] has been re-mapped to qwerty-P.

2.1 DreymaR's ColemakCAW layout for English & Norwegian: Backspace re-mapped to qwerty-H. [K] has been re-mapped to qwerty-O, [Y] to qwerty-P.

This is the one I'm actually using, as I type in both languages. The positioning of [K] and [Y] is not completely optimal but is, I think, a good-enough compromise.
All else is the same for all three layouts. I've followed Steve99's advice and re-mapped qwerty-Caps as Alt Gr: this makes it possible to have all the most important symbols— " ( ) ! ? etc. —along with the modifier key itself on the home row. Qwerty-AltGr has been re-mapped as Alt so as to have one Alt key for each hand. The various symbol keys I've left mostly empty; as far as I'm concerned, their positioning is not all that important, and people can just re-map them as they please. (But then again, I'm not a programmer, and having had to work with various national keyboard variants I'm not so attached to them being in specific places anyway.)

Hmm, interesting. What if you were modify this one slightly to have J in the Qwerty B position, and K in the Qwerty Y position. That would preserve standard Colemak fingering pretty well. It would also mean the infrequent J and K would be in the two worst positions while the all other non-index finger keys could remain unchanged.

Thanks for the replies. I didn't realize there were any before yesterday as I was expecting to receive e-mail notifications... Oh, well.. As I mentioned in another post, I ended up following DreymaR's advice to go back to my original and less intrusive change, which was simply to put Backspace in qwerty-Y and move J to qwerty P, while otherwise adhering to his ColemakCAW layout (my apologies if I've got the name wrong; I'm still a bit unsure whether or no W-Wide only refers to the version with the right hand characters moved one key to the right). The colon and semicolon I've re-mapped as uppercase of [ . ] and [ , ], respectively, which is their normal position in my native Norwegian. Although this is not relevant for me anymore now, my reason for not wanting to put K in too poor a position is that, with a frequency of 3%, it's a fairly common letter in Norwegian. I swopped Æ and Å because I wanted Å, at 2%, to have a better position than Æ, which has a frequency of only 0.2%. My muscle memory for these letters was never that strong to begin with, so it doesn't seem to have caused too many problems.

    Ayway, as with all changes, the latest one did come with a price tag. It wasn't too bad, but from now on I'll probably abstain from any more re-mappings (except for the symbols), at least until I swap my physical keyboard for something else—perhaps a Texblade :) ... At the moment my typing speed seems not to have improved much beyond where it was before I made my first set of modifications a month ago, so for the foreseeable future I'll probably need to focus on practising and getting familiar with what I've got.

I meant to include a couple of images below, but I'm having problems with upgrading my drawing app on Google Play Store. Will try again later...