I am not familiar with a 'one thread per person' rule....maybe you are referring to the rule that similar marketplace items should be consolidated into a single thread.
Yes, the Marketplace rules. Services can't have multiple threads and individual sellers can't have multiple threads to sell or promote the same thing.
If you are selling the same thing via multiple accounts *AND* are bumping each accounts' respective threads every day, then you are, at a minimum rubbing up against the one bump per 24 hours rule.
This is exactly what he's doing on multiple main accounts and countless other newbie accounts who's sole purpose was to bump his thread by either feigning interest or faking a trade then leaving a fake vouch. He's also leaving feedback with his alts (not against the rules but pretty scammy (and then there's the dozens and dozens and dozens of hacked accounts he doesn't seem to want to answer where he got them from)).
I guess my concern about mandating that you can only sell the same item via one account is that it gives incentives to not take unpopular stances on issues, which is anti-freedom of speech.
I don't see how this would be anti-freedom of speech. You can have an alt to post 'controversial' optinions or sell something if you don't want it associated with your other account, but there's no good reason why you would need multiple accounts to sell the exact same thing other than to spam advertise which is exactly his intent.
For clarification, I don't disagree with the OP's ban, assuming that what you say about him is true (or mostly true, if he is able to poke a small hole in what you say).
He's just just clutching at straws and trying to wriggle out by a technicality on
one of the
many rules he broke. He doesn't have any excuses. Never known a user like him.