In regards to "comments should be a plugin", that ship has sailed. If that goes through, we might end up in a situation like the link-manager, where it is just rotting away in WP Core and people have to choose which of the different plugins they might want. I suggest to leave it in Core and develop it further.

I do agree with cleaning up the settingspage, and one button "to rule them all", with comments fully off or not.

By the way, I do like the status of "maybe spam" but is that not practically the same as "pending"?