Thanks so much for the LDT link, it's exactly what I was looking for (and thought impossible).

I can't speak for the GP, but my problem with ACE et al. is that they replace the textarea with their own HTML structure (e.g. a div for every line). I understand the reason why, but it means they have to reimplement all the textbox behaviour and they never get it completely right.

For example: when I double-click on a word in the textbox I'm writing this in, and then middle-click somewhere else, the word gets pasted there.

In ACE, it pastes a different text in a different location.

ACE is brilliant if you want to a full-fledged text editor. But it's an overkill if all you need is a normal textarea with some colours.