Just upgraded to 3.1 and I was hoping that the comment_form_title() function would work already. Still doesn't. Specifically, it doesn't follow the 2nd parameter ('Reply to %s'). It does follow the 1st one, though. Accdg to the codex, this function only works for those whose sites don't call comment-reply.js - my site does call that script, but how come the 1st parameter of the function is being followed, and not the 2nd?
I saw that the other thread about this issue (here) has already been closed, but the problem still exists.
You see, for me, even if the replty-to-comment box will appear directly below the original comment, changing the header text is still necessary. I have a food blog where the heading for the normal comment box says "Post a Review", because presumably, I expect my readers to voice out their own thoughts about the restaurants I've reviewed myself. But when someone replies to an existing comment, "Post a Review" does not sound right anymore, does it?
It's your theme. Works fine on mine.