It is not appropriate to advertise in most online spaces for much the same reasons it is not appropriate to barge into a restaurant and walk from table to table peddling your wares to the customers. Spam is not an acceptable "business", and discussion spaces are not a plaform for spam.
The problem is that if you get hit with hivemind moderation in M1, then you're likely to see it rated as fair in M2. This is encouraged by the "Troll" and "Flamebait" options which can be slapped on any dissenting opinion.
Moderation is fine, but it must not be confused with censorship.
Moderation is when stuff is filtered out for you, because you don't want to see it. If you got to see it by mistake, you would agree that you didn't want to see that - maybe because it was factually wrong, maybe because it was disgusting, maybe because it was just irrelevant. Doesn't matter. All moderation is justified in terms of what the user wants to see.
Censorship is when someone hides something for you, because they don't want you to see it. Maybe because they're afraid it'll turn you into a racist, or into an idiot, or into a slave of consumerism, whatever. Doesn't matter. All censorship is justified in terms of what it will do to the minds of the recipients.
Now, maybe there are some people who are afraid for their own minds. Who are afraid that they will turn into a racist, if exposed to racist propaganda, for instance. But it can't be many. So there's little actual overlap between moderation and censorship.
The distinction you are trying to make is impossible to make in practice.
I don't want to see holocaust denial bullshit. Others might not have a problem with seeing it. Every sufficiently large space will contain at least one person who wants to post it and is therefore OK with seeing it. Is it moderation or censorship when a space I share with those people decides not to carry such content? The mods may not want to see it, and as it happens I don't want to either, but I've not actually /told/ them I don't want to. They've simply assumed on my behalf.
The same applies to any subject you might pick, no matter how controversial.
There's no per-person per-subject way to opt-in or opt-out that can possibly scale. I don't want to have to supply every online space with an exhaustive list of horrible things I don't want to see; and flagging after the fact doesn't solve this either since I also don't want to see those things even once before I get a chance to express my desire to not see them. Those cookie opt-out boxes with giant lists of vendors that everyone loves to hate? Imagine that but everywhere and for every subject. That's what exhaustively expressing my preferences would look like.
One approach that does scale is to allow the owner of a space to make filtering decisions on my behalf, and if my preferences don't match theirs in a way that is important to me, well, I can go elsewhere or make my own space. This is what we have now. But it's still someone deciding for me what they do not want me to see; they may or may not have my best interests in mind, but in your proposed classification, this is censorship.
Worse, though, some people /really/ want to parade stuff I don't want to see in front of my eyeballs - they believe the problem is that they are simply not shouting loudly, frequently enough, and if they were just allowed to preach to me one more time, I would convert. Compare the person elsewhere in this comments thread arguing for their right do "do business" everywhere currently moderated. Those folk are strongly motivated to make arguments containing combinations of words that will result in their bullshit being paraded in front of my eyeballs yet again. They will try feeding different combinations of syllables to the owner, the moderation team and/or anyone who might exert pressure on them, in the hope of rules being relaxed. One such possible combination of syllables is "This is censorship! I am being censored!" It may even be true, for whatever definition you prefer! Regardless, it will be attempted. For some, it's their hobby and/or job. They devote all available time to doing this. Slow drips of water, given sufficient time, wear down stone. If I don't push back even a little, all spaces I frequent will become filled with content I do not want to see. Is this censorship? Am I a censor?
Personally I see the moderation/censorship divide as one of those irregular verbs English is so full of, conjugated approximately like so: I am making my preferences known; you are moderating; he/she/it is a censor. The "our glorious homeland / their barbarous wastes" image frequently seen on social media is another good analogy for what frequently happens.
At the end of the day, though, call the practice what you will, but despite our best wishes, entirely uncensored spaces do not look like a university agora filled with enlightened folk freely exchanging valuable ideas for the benefit of mankind. They look like 4chan's /b/. I am glad such spaces exist, but I would be very sad indeed if every place on the internet was like that.
In many cases it's easy to make the distinction. Many will not hesitate to admit that they suppress things because of the effect they fear it will have on the audience. Not just the effect it will have on the appeal of the venue, or the image of the company, or whatever.
And I'm not even saying all censorship is necessarily wrong. There's one very obvious case where you keep people from seeing things because you fear the effect it will have on them (which is censorship), but it's generally accepted, and that is when the people in question are children.
Yeah, it's hard to judge people's sincerity. Do you really just worry that your space will be overrun with nazis/terfs/communists because you don't want to see that shit yourself, or are you afraid that they'll convince others? But that doesn't mean the distinction isn't worthwhile. Most of all, it's necessary to apply to yourself. It's a critical question you have to ask yourself, if people trust you to moderate for their benefit.
> Most of all, it's necessary to apply to yourself.
Sure, that sounds like it could be a great principle. It's not what actually happens, though. The terms are loaded weapons, sticks to beat people over the head with; and discourse online trends weaponised. Cries of "censorship" are used as a battering ram to prise open an online space for invasion. When the only difference between an action that is morally acceptable and one that is not is the internal state of mind of the actor, with the case being tried in the court of public opinion, defense is all but impossible.
You did it yourself: "Censorship is when someone hides something for you, because they don't want you to see it." Someone. /They/. That's not a sentence about personal introspection. That's a statement tying a judgement to someone else's actions. He/she/it censors.