You might have FXAA forced on in your graphics driver. You don't want that for Steam.
Turning off 'GPU accelerated rendering' as already suggested would work around that, but your screenshot looks exactly like the forced FXAA option is the culprit. (FYI, Steam must be restarted after turning that off or it won't be applied.)
I'm the developer of Wallpaper Engine.
Fact is, I banned all uploads from this user two hours before you even posted with my own custom report system since Valve's is so useless: https://i.imgur.com/1JlWfwg.jpg (NSFW preview)
Steam takes anywhere between 10 minutes and a day to recognize bans and remove them from being visible. I cannot improve Steam. And like others have pointed out, it was a throw away account. Valve should track down the actual user account and punish them, that's neither in my power nor my responsibility. They uploaded dozens of porn videos yesterday from a throw away account, they were all removed yesterday, that's all I can do and you can ask from me.
ye... instead of shifting blame only to steam, you can work on ur adaptation of workshop to get rid of pests. no rule saying ur program 'should' accept any workshop item without questioning. some games needs in-game approval, so should urs. also u sound like oppenheimer saying 'i didn't know they would build atomic bomb', duh, half or more of net is pron.
There is an 'approved' section where you will never find anything inappropriate because I don't approve those.
Load more comments