It's hard to believe that you don't know why it's an asshole move to advertise under someone else's work, and if you are that dense the lemme explain. Imagine you just made youtube video then you get comments like "my videos are better than Dreamvoider's come check out my channel plus theres a 15 dollar fee after watching 3 of my video's"
Meh, I can believe it. He can post in Discord because he's obviously a patron, but instead he posts spoilers here, when he should know that many readers here have not seen the update yet. Even posts direct public messages to dev here, when he must know that Discord would be monitored much more closely and be more likely to get him a response. The self-absorption necessary without resorting to malice is considerable, but I think he's capable.