This one is for the full mods/staff I guess, if I suspect two accounts on this site to be owned by the same person, is there someway to communicate that so a full mod can look into that? Is there maybe a thread for that already? Or is that maybe (a) not relevant or (b) not against the site rules? (since it's "just" kind of a secondary account and not ban evasion). Just curious, thanks in advance :)
As long as one account isn't banned for doing something, then having alternate account isn't against the rules. If however they are using the alternate account to circumvent a ban then it is against the rules, although you'd likely not know they were the same person unless they did the same stupid things.
I think they should only have one record for a game between all the accounts though, so both accounts can't have a record for Game X any%, but it's something you'd talk to game mods/site staff about.