Quote from Baron:
The problem is not the name change. Once I make a change to a username, it would be reflected on all posts that user has made. However, any posts of that old user that were quoted in the posts of others would not be changed. So for everything to be consistent, I would have to manually search for the posts of other members that contain quoted passages from the old username, and then I would have to edit those references manually. I don't mind doing that for people who only have a small number of posts, and therefore a small number of quoted passages in other people's posts. But when someone has 100, 200, or more posts, there are likely going to be a lot of quotes that need to be changed manually, which is way too time consuming to justify the effort.