I just say let them do what they want. It hurts no one. If it annoys you maybe you should work on that. It a style, a personality. Now it they start demanding you do the same then maybe it's them with the problem.
If this is their "fun" why should they need to stop.
Just sitting here now and someone came on with their phonetic call sign just to say they were on the repeater. Not talking to anyone. Didn't bother me.