EDIT: per JK, mods can't check games like this. Then I see two avenues: using the query game API to find QM games since Ozijs joined the site with his 2nd account and seeing if any of them have both Ozijs and one of his alts (this is doable by any Member, but impractical); or escalating to an admin (or Fizzer) who might have the capability to investigate.
Honestly, if the query game API approach would mollify your concerns, I could do that over the weekend...
TL;DR: Quickmatch is not meant to be taken seriously as a competition. Its only purpose is to get you a quick match.
Well, you could still file a report so the mods can (presumably) check Ozijs (and his alts') game logs to see if he's ever played himself on Quickmatch. That's what I would do I if I were in your place and had those suspicions.
I am saying that there are a huge amount of ways in which you can game the system of this site using multi accounts in ways not predicted by the rules
Yes, there's a balance involved. If you look at the other online turn-based Risk-like mulitplayer game sites, you'll notice that they pick the opposite presumption: Conquer Club/etc. ban players for multi-accounting, even without any gaming of the system. That creates its own set of frustrations (see:
https://www.reddit.com/r/conquerclub/comments/a042i8/very_unwelcoming/). I, for one, appreciate Warzone's permissive alt policy, because the frustration of the other approach is much worse than the cost of low-profile gaming of the system. It's honestly very hard to meaningfully impact the outcome of a competitive event through detectable multi-account use, especially since competitive events are small enough to enforce alt policies. (If you join the MTL on an alt, you'll stick out.)
killing everyone else's rating with "low" rated alts
This is inevitable if you play QM with multiple accounts. Although honestly the impact of this sort of stuff is negligible relative to normal fluctuations in QM rating (if you look at the top 50 SEAD/SE1W QM rated players, you'll notice the active ones have ratings change by dozens of points daily).
The end-game is just that no one who plays seriously takes QM ratings seriously. But that's negligible, because QM ratings- like Min34 pointed out- aren't skill ratings at all anyway, due to the modifications QM applies on top of the TrueSkill rating system it uses.
Ozijs reputation as a top SE player does not come from his QM rating, just as Rene Descartes is not considered among the best players on the site in spite of his astronomical QM rating. QM rating leaderboards are nearly meaningless already.
Still I think he his a cheater and he should not be allowed to play with 5 accounts in the same competition, but I am a small minorance it seems.
This difference of opinion stems from the rest of us not viewing Quickmatch as a competition in the first place. Quickmatch is just a casual way to get a quick match, nothing more. If you want ratings/rankings with competitive meaning, you need to get them from the ladders, Clan League results, and P/R leagues.
Edited 9/30/2021 20:23:50