I am new to Stack Overflow, and have quickly found that the comment box (that is, commenting on someone's answer/suggestion) is really, really, really bad.
Hitting Enter while typing results in the "accept comment" button being hit. What? Am I supposed to type HTML code for CRLF? Is this slashdot? This is terrible design.
No formatting buttons. A new question or answer has all kinds of formatting exposed. But the comments get none. This is bad. It makes it more difficult to comment on a suggestion with blocks of code or other formatting.
It automatically turns typed text into "friendly" text. Example: If I type a URL into the comment box, it turns it into a link and removes "http://" from it. That isn't what I wanted. I typed what I wanted, and then the site went and mutilated it.
Overall, I have to rate the comment box 0 out of 10. It's not only incredibly lacking in features, but it actually mutilates what I typed into something I didn't type, without even asking me. Bad. Just plain bad.