Sometimes I change my username on the MSE site. and it cause a problem. for example for my older comments on posts when I discuss with other users in comment section we normally tag usernames in the comment. but now with my new username I see some older comments that other users mentioned my older username.
It makes things confusing for everyone who read the discussion because they see a username mentioned that not exist anymore. I think it is a good idea to solve this issue somehow. For example, if usernames mentioned in the comments automatically contained with a hyper link to the homepage of the user could be useful. Or if mentioned name in the comment automatically could change, to me it was best solution (although I think it is harder to bring this feature to the site).