

The person who posted would be the moderator for that post.
In theory a moderator is expected to be neutral in regard to what is being posted/shared (be ok with conflicting opinions, for example, even ones that completely oppose the OP). At least, in theory.
Someone posting something will seldom feel neutral regarding what they just posted.


Imagine this: I disagree with your reply (not saying I do, just pretend I do), and since I’m also its moderator, I simply delete it (and if you repost it I block or ban you. And that would just be me not liking someone daring contradict my own little comment.
More seriously, I think this would be a real huge source of trouble: people IRL already have a hard time to stand critics. That’s worse online.