I was looking at an old election page, and I noticed that I am able to add comments, as well as the other standard moderator actions for comments (deleting, editing, etc.):
I clicked "add a comment", fully expecting it to not work, and yet when I reloaded the page (while logged out), I saw my comment there. I haven't tested editing or deleting other comments, since that seems more destructive.
I suspect this only works on sites I moderate, since when I checked another site, it does not work. For reference, here is what it's supposed to look like: