@it33 , so, something kind of odd happened. The image I uploaded in my original question isn't valid anymore, and the problems there are gone....so yaaay. Now everything in the chat pane is centered. It's also that way in the gitlab.mattermost.com/community site, so it looks like a problem on my end for sure (unless that's the new design).
the chat being centered isn't expected behavior is it? It's not bad, just different, and since I was already having issues, I just wanted to make sure I didn't have something broken.