I agree with you that FLOSS doesn't mean automatically better and there is no reason to wear a tinfoil hat. You ultimately have to trust someone if you don't inspect the source code yourself. I was just saying that being revol centralized and having access to every information isn't the best design for a discord privacy-respecting alternative, but they do have a good privacy policy, so if you trust they respect it (atm no reason to doubt that) then it will be surely better than discord. Discord does collect chat history though. On discord privacy policy:

Information You Provide: We collect information from you when you voluntarily provide such information, such as when you register for access to the Services or use certain Services. Information we collect may include but not be limited to username, email address, and any messages, images, transient VOIP data (to enable communication delivery only) or other content you send via the chat feature.

They don't say that they sell said information for advertisement (even if they send some data to third parties) and I don't have seen any report about them getting caught doing that, I'm sorry I assumed. But I admit I get a bit carried away with doubts about companies who offer closed source software to a very large userbase. If there is a chance of making more money, they usually take it.