(Yes, I know I’m gently steering us away from window shopping for Git frontends. That’s called “taking a step back”.)

Right, Discourse isn’t a full replacement for a bug tracker. It’s more of a solution to the problem of people relying on proprietary chat platforms than the problem of relying on a proprietary platform for software development. But many of the arguments seem to apply equally, particularly the concern you expressed about sharing personal information or having to maintain an account on an unfamiliar service. (Discourse’s UI is also much more comprehensively localized for a global audience than GitHub’s, which isn’t saying much.)

Some projects do use GitHub discussions, but that feature tries to replicate Stack Overflow post voting just like this forum’s post voting plugin, with all the attendant confusion. I wouldn’t recommend it.