I get what you're saying but I never said this system should be mandatory.
> [rumors of 35k]
There is no marketplace like itch that supportive of creators, so there has to be a way that workload doesn't increase in an unsustainable way for itch.io too.
> But I think billing devs for having poorly educated (or poorly behaved) customers is the wrong approach to the issue.
I think very differently about the issue. In my opinion it's almost never the fault of the user if software is difficult to understand / install / remove. And almost always the fault of the software. (for reference: I'm not selling video game, so I may have nicer customers).
It's not like customers write emails out of boredom, most of the time . You can also lessen the support load by 10x with a FAQ page or easier to understand design.
So the support load amount is, in some capacity, controllable by the developer. If itch.io does support for free, then it's the responsibility of the developer to try to lessen that support load. And if they don't, get charged for it.