I don't think it's driven people away so much as made it near impossible to comment with any sort of confidence.
I can tell you for a fact that I have written dozens of spectacular comments that have been swallowed by the hard fork.
Well, maybe not dozens. At least two "Nice Post" comments.
It is not that it drives people away, but it makes people think about commenting. The lack of "confidence" is an issue.
The other thing is the comment count - which takes away the indication that it might be an interesting post :D