Strange situation but possibly a reasonable conclusion to my query. After War had finished today, I kicked 6 inactive members from my team. We're an open team, so 6 new members joined. However, I noticed 3 members who joined instantly were named MonsterMaster1234 (as an example, all had 4 digits at the end that varied).

We have a Level 20 limit and 2 of those were Level 17, so I kicked those and 2 more joined. Again, MonsterMaster**** joined along with another, different variation of numbers at the end.

Is this something anyone else has encountered? Or know a reason why there are multiple accounts of the same name?

That is the name which system gives I think. Until you add your Facebook account or Rename your Profile name. The Name will be Monstermaster****

And I thought something suspicious was happening. All makes sense now! Thanks for clearing that up, I've just never noticed it before