Also, what I said, people do take screen shots or just repeat information you gave them there.
Nothing can protect you from that, no service or technology, you wiilingly gave that info away. But are you telling me this is actually one of the reasons Itch won't implement the feature? If so, that would be a "reason" not to have any private messaging system, anywhere.
Did you see your proposed solutions anywhere on the net? (I am talking about a public website, not some system like discord). Also, did you see anyhwere a private message system that is disabled by default (or enabled, but can be disabled)? I am curious, how viable those solutions are. If they are, one would think, that they are used at some places.
Not very familiar with a lot of other services, but that takes nothing away from the potential viability of the propsed solutions. Don't see why PMs could not be disabled by default if that means they would be introduced to users who want to utilise them. Keep in mind, Itch is obviously not most of the platforms, otherwise this kind of feature request wouldn't be an issue.
And no, a block list will not prevent spam. Users would have to block each spammer after the fact. That is not prevention.
True, I should have worded that differently. I named the allow list first for that particular purpose. Block list would be a mitigation technique for users wanting to go the other route.
Imho, itch is designed for publishers to interact with the players, not for the players to interact with each other.
How about players interacting with the publishers non-publicly and publishers interacting among themselves, an example Dace posted in another comment?