I can join the server with my USGN ID, or with Steam, or with both. And it doesn't mean if I once joined with both and then I will join as same as always. I could join with only USGN ID or Steam later.
So what if I'm gonna save some data of that player?
He joins to the server with USGN ID first, and then I save his data for his USGN ID but he might join back with his Steam account and could say "Where the fuck has my level gone?".
What should I do about it?