I worked for a payment processor in Europe, we provided SEPA and some other payments, but not card payments (so there could be some difference).

Difference is in fees and licenses. Payment processors that process high risk payments (adult industry, gambling, etc...) have higher fees and need license from governing body (usually a national bank in country where the payment processor is registered). So if you process high risk payments as low risk you will get a fine from governing body and you risk to lose your license. And if you don't have a license for high risk payments you cannot process them.

I don't work there anymore, but I heard they lost SEPA license a couple of years ago because of risky transactions.

Now I am not sure if Visa and Master are forcing payment providers to give up high risk transactions or if they are forcing them to classify all transactions as low/high risk.

There are none that are reliably usable by actual porn companies at this moment. Check pornhub, you can only subscribe to them via bitcoin and direct bank payments.

> Question: what prevents an organisation like Kickstarter from using more than one payment processor, including the ones used by actual porn companies?

The way the policies work, they would either have to use the latter processor for all transactions (which would be prohibitively expensive) or relegate all "adult" content to a completely separate company and domain, which would be a huge pain and expense to operate for something that constitutes a relatively small fraction of their business.

Nothing prevents them, and some companies that want to support both adult and non-adult content do. But it's also reasonable for Kickstarter to decide that adult content is not so important to them that they want to jump through hoops to dodge Stripe's rules.

That's what I want to know.

The fact that if they don't ban it, Visa and Mastercard will blacklist them and they have 99% of the market share.