What would be nice is if a moderator could flag posts as "this is a moderator post" versus "this is me as a user post" which would solve the problem. For example, I should have to see any posts by user XX who is a board moderator if they are actively moderating, such as "please don't cross post blah blah blah." But suppose I don't agree with that particular moderator's political views? Those posts should be hidden from view.
As a quick and dirty solution, add a flag to the posts table called is_mod_post or something like that. When a moderator enters a post that is a part of their moderator duties, they click the box, and that post is guaranteed to be visible to all. But when they're talking about the upcoming election, they leave the checkbox blank, and the post is hidden to those that have added the moderator to a foe list.
It is my opinion that a board administrator account should never be used for casual posting
, and therefore all administrator posts should always be visible. For example, you log in to a *nix system as "root" only for administrator tasks, not for casual use. However, many (if not most) board owners don't subscribe to this, and the board admin / founder account is also used for regular user posting. In that case the same checkbox could be used.
An additional benefit is that when is_mod_post is true, the post can be formatted / styled differently to make it stand out.
But ultimately that way a user can "foe" a moderator while still seeing moderator posts. If a moderator abuses the checkbox, then they can be removed as a moderator.