Has it changed much?
The major change that sticks out to me is that each comment is now placed in its own html div, so minor html coding goofs don't cascade through the thread.
Back in the old days it was fairly common for someone to forget to turn off the italics if they italicized something, resulting in all the subsequent text being italicized. That lead to frequent postings of "Italians Off!!" when someone posted the html code to turn it off.