Adding yourself back to a group iMessage?

So, I am in a group iMessage with some friends and whenever we kick one person out of the group chat (it's the same person every time) he always seems to find his way back. By this I mean, HE ADDS HIMSELF BACK.

Does anyone have a explanation to how this occurs? Is it just a glitch in his iMessage or is this something that I can also do?

I know this sounds like I am a complete newbie to the world of iPhones, but I can assure you that I'm not. I'm aware that normally you can't re-add yourself to a message like this and I've probably explored most of the options to try and find my own solution to how this happens, but I can't place my finger on it.

If it helps at all I'm pretty sure that we are all running the latest ios 9.3.2 update.