A lot of BBCode has been updated for the 7.7.x series to produce more optimized HTML. There wouldnt be much of a server performance boost in rebuilding the content. But you will get cleaner HTML pages with a somewhat smaller database size. More work has gone in to trimming of the BBCode=>HTML heft for 7.7.4.
As for new posts being less quick in the return to the forum/postlist, What else may be causing that is if you only get a single new post (or login) once every few weeks, and there have been thousands of bots who've been spidering your forums, triggering the Post View update counters to update/purge. That is one of the jobs performed when a new post is created, or a new login is successful.
During the past 5 days, you made several post about being DOSSED by bots (thousands per minute). If thats still happening, those bots could also be triggering the Post View counters, among other things.
