Regular Expressions can do an awful lot in the arena of text processing; but a lot of what an editor used by programmers needs to do can not be done at all, or at least very well, by over reliance on Regular Expressions.
While I agree with the desire for ever more powerful mechanisms, I'd like to speak up quickly just to say that what Allan has effectively created with the scope system, used both for styling and for commands/etc. is a real parser -- a CFG or set of CFGs -- not a mere regular expression, because of the ability to nest elements in a language grammar. Just like in a conventional machine language parser, regular expressions are used to recognize individual parse elements, but the structure it generates and uses to analyze and represent the code or other file contents is context-free, and hence just about as powerful as anything used in other editors, even up to the level of Eclipse's fancy-dan refactoring tools and so forth. What could make this more accessible for more advanced tools might be a more direct API to run over (and potentially transform) the parse tree, not just the current context, but what it does now is still much more powerful than mere regular expressions. -jrk