FAQ 148 should have something in it that says that the comment per post limit is 5,000 comments.
This came about from two support requests here and here.
Thanks to xnera for some CVS digging for this one :).
Went back a few posts in the comm and couldn't find anything else which suggested this change. So whoops to me if someone already has. Poke and I'll fixx0r this post if need be.