People change their names from X to Y, but their older name is mentioned in answers and comments (like "as X explained in his answer" - while there's no link to the answer that now is signed by Y).
A better solution would be for the user's profile to have a field listing the older name, for some number of days. (30 would be reasonable.)
When referring to a post rather than a person, it's usually best to link to that post. Of course, not everyone does that. (This is something people may wish to consider when changing their names.)
I think this is related to me changing my name. Consider what happens if that takes place. I have 500 questions/answers combined. They don't need to know when I change my name. It would be a nuisance.