A feature I've never seen anywhere but would be great for writing CGI code, would be the ability to type in or paste in HTML code and have it automatically escaped properly i.e. all the backslashes inserted where you need 'em.

How about when the HTML code includes JavaScript code??? I'd be impressed with any editor that managed the escapes correctly then!

Done that? OK, next, regexps that work on JS code! (I sometimes use LWP to get HTML pages and repost them with the JavaScript amended. That leads to some very, very nasty regexps.)