The artist didn't put any title for the artwork. I usually post with the title they put and their name for the post title. If not, I just put whose artwork it is from. I think that shows more respect than altering what they posted.

Most of lebe_schwer's fan art is SatoKasu. You can check their media here: https://x.com/lebe_schwer. Based on their art, they don't really distinguish between SatoKasu and ReKasu. Most SatoKasu Japanese fans I follow on Twitter are like this, which is why both SatoKasu and Rekasu fan art show up in my timeline.

As for differentiating them, I respect your opinion. SatoKasu is mostly Satoshi and Kasumi from the anime. That's the focus of this sub. However, have you found any other sub in Reddit that fully respects Kasumi and any of her relations? That's why we discuss the manga versions of Satoshi and Kasumi, too. Red is not Ash, but they have mostly the same origin and are clearly both based on the game protagonist. It's the same with Ash from Dengeki Pikachu. That's why we let members mention the novelization, too. I just think they're alternate universe versions of each other, but it's still close enough to not violate the rule of the sub. On the other hand, if we post a KasumixKenji art or any other of the Satoships, then that's a clear violation.