I edited the OP to reflect the updates I posted as a draft earlier.
Would it be OK to have a signature linking to a blog/article explaining what mixing is, how it works and containing URL link(s) to mixer(s)?
It'd be OK in a post. In a signature it would probably not be allowed, as it would look like "promoting a mixer".
It's OK.
To allow efficient communication of mixers with users for support reasons, I would propose that an "official" discussion topic about every mixer could be allowed, but without any advertising elements. And the accounts representing the mixers could have to limit themselves strictly to this "official discussion/support thread".
Sorry, but having official mixer representatives do that sort of thing is too problematic, so that won't be allowed. But a non-mixer-representative creating an "ASDFMixer discussion thread" would be OK.
I believe either you ban ALL Mixers or you let them all roam free. Know Your Customer being one of the ways you separate 'good' from 'bad' Mixers opens up a way for more BAD things than good things to happen in the future. It includes and opens up ways for more of the bad guys.
Before, I didn't really understand your position on the KYC issue at all, but now I understand it a little better: You see KYC as fundamentally bad, and by "favoring" KYC services in any way, it supports the existence of "KYC-only zones", possibly diminishing "non-KYC zones".
I agree that KYC is bad, it'd be better for no service to have KYC, and KYC almost entirely exists because of real and threatened violence by the state. But I still use a few KYC services, and I don't see doing so as really "supporting the KYC ecosystem". If a big company like Coinbase created a KYC mixer, I could imagine myself using it in a few limited cases. True, a KYC mixer would only have value because of the evil of state-imposed KYC requirements, but it'd still potentially be useful. (In cases where I don't want
anyone to be able to link my transactions, I wouldn't consider a centralized mixer in any case, KYC or no.)
I don't think that criteria 3 will really help any service very much, but if hypothetically removing criteria 3 would prevent KYC-mixers from existing anywhere on Earth, I still wouldn't do it. KYC-mixers would probably provide some value to some people. It's like: would you want to ban all patent-law lawyers just because you don't think that patents should exist (as I do)? Moreover, I prefer to ban as few things as possible, and this is something that doesn't
need to be banned.
I did edit criteria 3 to make it clear that I'm not
endorsing KYC.