though more often I just de-italicize the emphasised word.

I do prefer this, though sometimes I wonder if it's really...noticable. If you want the word to pop, you want something about it to be different than ordinary text. But I stick to just de-italicizing because, as you say, the page can look busy with a bunch of these things going on.

And I will sometimes use specialty punctuation to indicate telepathy as opposed to regular speech--

I forgot about that! I HAVE seen that in published fiction...I think Mercedes Lackey used italics within slashes to denote telepathy/special communication. Or maybe it was colons?

And back when I was posting to non-HTML mailing lists a lot, I would use = to indicate "This would be in italics if I could do italics in this format, but I can't, so you'll have to imagine it."

Yeah, I totally forgot to mention that some of these conventions come from posting HTMLess. I totally used stars on lists and on ff.n back in the day before you could easily use italics. And while it kinda sucks, I have less of a problem with it when there's no other way to do it.

And completely with you on the using some of these things more than I should...I only use italics, but I know I overdo it.