I understand why you guys would suggest not to allow this, but for my forum it is essential. I run a pool league, where members change their username/playername very often. I have run my current forum like this for 5 years now with no problems. I just recently bought vB and am currently working on switching my old forum to vB.
Threads and forums do not get out of sinc by changing usernames, as they go by userid.
Thank you MisterPopularity for your reply, I will search again for this mod....though I couldn't find it before. As for logging the changes, that's not needed for me