I love Discord's interface overall. It's really nice, and makes it easy to do all kinds of things. The feature set is excellent for a monolithic application like this.
> but thinking it's usable is beyond my capability to understand.
This is part of why UX is so often trash in FOSS projects: a lot of FOSS enthusiasts cannot even perceive the usability issues that exist in them. They're on a completely different wavelength compared to the average user. They are, in other words, UX-blind.