Essentially, Steam (check rule 15) and itch.io are getting rid of/delisting content that payment processors don't want to process. (It's mostly adult content.)
This website has more information on what will happen if you own a game that gets delisted, and how to get it back if at all. I would personally recommend downloading it and backing it up somewhere, especially for itch.io which is not listed on the website.
A video with link sources for its information in the description validates this. If you just want to click a link here instead of going to the video, here's one for Steam and one for itch.io.
If you would like to protest this, https://yellat.money/ works for anyone and Americans can take action at https://aclu.com/mastercard.
Please remember rule 5 and tag NSFW content as such. Discussion of NSFW's existence is fine, getting into details should be tagged.
Thanks for putting this together! This is an important matter so I'm pinning this thread for visibility.
On a personal note I'm definitely downloading my itch.io library - while none of my games there should fall under the current purge I'd rather not risk it. Steam should be safe as, as far as I know, they don't really have a tendency of removing purchased games from people's accounts (even when delisting titles) but I guess we'll see.
Besides the obvious issue of having to keep constant vigilance about our freedom it's also a good reminder to keep backups of anything you don't want to lose access to. It's the only way to be relatively safe from things like this.
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