They also are unusable with spam and origin filtering. Not getting a message you were waiting for? Turns no message from that service is getting through, no notification, no nothing.

This is actually true, I can’t get any email for one specific Substack I paid for (and others work!). And since they do login by email I can’t log in at all.

Spam filtering is "keep you from seeing things you don't want to see". Moderation is "keep you from seeing things I don't want to show you".

That's not true. It's more that spam is automatic, and as such is easy to automate away. If someone replies "BUY MY PRODUCT http://product.link" on every post, that's spam. If someone is consistently shitty to other community members and generally acts like an asshole, that's someone who needs to be moderated away.

I partly agree. There's a skill and a moral quality internal to moderation, which means that good moderators will exclude the content they judge the community doesn't want without letting this judgement be swayed by their personal agenda. But bad moderation, where the moderator lacks the skill or the quality to do this, is very much a thing.