I use Markdown to write for this blog, and I don't think I could write much online without it. (Of course, that's not saying much lately—but nevermind that for now.)
Although I do appreciate all the effort put toward enhancing
<textareas> on the web, I'm not a fan of WYSIWYG writing interfaces. They hide too much in an effort to make things "easy"—yet, for all that ease, they make me miss Reveal Codes in WordPerfect 5.1 for DOS. Hell, I wish I could write books using Markdown instead of Microsoft Word. (And, yeah, I know that some O'Reilly authors have written books in perlpod—but that's a bit too far even for me.)
Anyway, I think the issue is that it really bothers me to compose HTML in the same mental context as writing prose—HTML is too much like code. Coding and prosing are two different modes for me, and I don't like the constant context-switching thrash. (And, yes, I've just learned today that prosing is a word.)
So, apropos of this, there's been a thread in the blogophere lately naysaying non-HTML, wiki-text, and smart-ASCII formats. They seem to be mostly attacking the idea from a technical perspective, where it's more like a usability problem to me.
I don't see where Jeff Atwood's "Is HTML a Humane Markup Language?" makes the case for HTML as humane. As far as I can tell, the inhumanity is that markup schemes are harder to keep track of than HTML. Yet, there's a kind of coder macho thing going on there that's decidedly not humane—i.e. real programmers should be fine with getting their eyes poked by angle brackets on a regular basis.
Anyway, I do agree that some of these formats are horrendous. Wikipedia markup and BBCode are nasty in particular. Though, Wikipedia markup at least has some semantic purpose beyond HTML. But, I can't follow from that to seeing how the whole idea is wrong.
Perhaps I've said too much.
Anyway, I'll expend as many brain cells as it takes to not need to compose raw HTML by hand in the course of writing. As it happens, I can usually just use Markdown, so those brain cells were spent years ago. And thus, I feel I've saved more brain cells in avoiding coding/prosing thrash. So, it could just be personal preference, but I agree with the reasons why the original wiki doesn't use HTML.