Thank you for sharing this, and thanks to HH for this thread. I read about this on a forum for developers but there wasn't much detail, so I appreciate that you're trying to put information here and share what's being written on Discord.
Like some of the other devs here, I have not received this notice so maybe I'm "safe" for now? I've always had my revenue share at 10% as I appreciated what Itch was doing for creators and it seemed reasonable. My title is also free here so it's donations only, so my payments may not have many issues with fraudulent charges and card disputes.
I do wish, though, there was a greater level of clarity from Itch on the criteria they used to determine who was getting forced to the other payment system, giving the targeted devs a heads-up in advance, and allowing them to implement revenue share (assuming that all the devs subjected to this had their revenue share at 0%), and letting the rest of us know through official communications rather than the grapevine.
Sigh.
Edited: Realized I was conflating deafperv and HH Richards, so edited to clarify.