Oops I forgot to put this post in the questions category

There should be three dots at the top of your post and you can click “change category”. To answer your question I guess fandom just works like that (or I don’t know the reason for that), though there isn’t really a point for the “gray circles” other then to show they are a mod.

I believe it's because Content Moderators do not have any moderatoring rights on Discussions, so there's no point for them to have the grey circle because they can't even do anything.