Bug - Normal Name Problem

[Maxence]

Yesterday I see someone at 50 streak then after 20 min I again see he is at 70 streak. Then I have doubt on his skill and think that the player is a cheater. when I try to search that player account, there is none. Name of that player start and end with ++
After this I try to creat a guest account (username: ++123456789++). Then I log in to my main account and try to search that and its not showing on screen.
So long story short, user ID start and end with ++ not shown in add friend screen, player use this bug for some benefit (maybe)

 

[Bones]

What was the reported username you saw?

 

[Maxence]

What was the reported username you saw?

sorry I forget the user name but its start with ++ and also end with ++
Edit: So, Today I find another of same case and I have proof also.
-I crop the image because its too large for update
-When I tap on his (+++A+++) profile from chat it shows A as user name