12 cents on every dollar seems like an absurd amount of money, for a relatively basic microblog.

Have you ever had to do your own accounts receivable, fraud detection, government compliance, and subscription management?

No, but I have paid Stripe 3 cents on the dollar for pretty much all of the above. To be fair our business was much smaller than Patreon

This is absolutely false, Buy Me A Coffee takes a 5% platform fee and ko-fi takes 0%, this doesn't include the usual CC processing fee which is relatively minimal (Stripe rate).

Generally, their users don't need a platform, they need a payment processor.

If they didn't need a platform they could use Stripe directly.

If stripe had a better UI and would batch payments then that would work pretty well, yeah. As-is that would probably not work out well.

So you're saying that platforms are useful...

We're talking about payment processing vs. platform, right?

"Good UI" doesn't make something a platform.

Doing payments in a fee-minimizing way definitely doesn't make something a platform.

I've been under the impression that patreon makes a bunch of their cash from people selling nudes (and perhaps owes their brand popularity to the groups of nude sellers that were using them) and that stripe refuses to deal with anyone that does nudes (?)

Maybe, but that's pure profit.

This isn't like a newspaper, finding neither ads nor paywalls will make ends meet. They're not phone app developers, finding users will barely pay $1. It isn't an ad-supported business that can only make a fraction of a penny per user. Their moderation needs are at a pretty small scale, with most user accounts tied to known bank accounts. They don't have to negotiate with rights holders for copyrighted content and get taken to the cleaners. They don't have to store and distribute gigabytes of video per second. They don't face big customer acquisition costs.

Youtube and Twitch are doing a lot more work for their cuts.