Valve have added a new rule to the Onboarding guide for game developers, noting that payment processors get a say in what stays on Steam.
Newly added rule is:
Content that may violate the rules and standards set forth by Steam’s payment processors and related card networks and banks, or internet network providers. In particular, certain kinds of adult only content.
Diff of the new terms https://github.com/SteamDatabase/SteamworksDocumentation/commit/fddd59b5395cc3c1c74574650dbf5784612d0521
:/ payment processors strike again (slippery slope etc)
Patreon has similar restrictions. I’m not sure about itch. They all rely mostly on stripe for payments. Stripe gets to set a lot of terms, and switching platforms doesn’t usually change that.
I’ve noticed that enforcement becomes more of a thing the larger the platform
AFAIK Steam uses adyen for payments (at least that’s my experience every time Steam wants to verify my credit card).