It's been observed by all of us that generally lot's of users change their username frequently. It's OK and allowed on this site and users can do that at their will.
But that sometimes create problems also in identifying the exact user or person to whom we previously were knowing and is confusing either. In this case we might not be able to communicate with that users just as we used to as before unless we properly identify him.
So my question is are there any Stack Exchange guidelines regarding to changing of the username. For example informing the community about the change in notice for short period of time or Displaying all the previous usernames the user were having to Hi-reputation users if not to moderators only , and they can provide the info. regarding to this as required to the rest of the users.
And are there some other guidelines like how many times a user can change his username in specific amount of time. etc. or specific to Hinduism SE !
Note - The question only concerns about Display name or Username and is not related to Display picture.