I propose a fresh start based on markdown. The comment textbox would be strictly plain-text only, with all formatting and html stripped on paste - like most textboxes. Markdown provides a gloriously simple syntax already familiar to millions of users of Github and Stack Overflow. There are about 2 billion implementations in everything from Ada to Brainfu**. If you're unfamiliar, check out this example: http://en.wikipedia.org/wiki/Markdown#Example
(Oh wow look at this link extending on forever without any intervention from me). Basically, if I have to type
again instead of >, I'm going to cry.
Of course, I'm aware this is likely a very big undertaking, and to avoid upsetting current users, it would have to be optional. I just hope you'll keep this in mind for when there is a major software upgrade. Thanks.