If each user has their own WoT inbox relay, and the WoT is just local of that server, then there could be a simple approval screens for new pubkeys that reply to the user. The user could approve each of those at night in some simple left/right screen for ok, not ok. Then something to mass reject all the spams. Maybe some little tool to evaluate the video and image content and already separate into a list for easy rejection.

If the WoT is shared, I think an active moderation could be very cool. Similar to what I said before, but for all accounts at the same time. Which I think is already happening in some form in existing WoT relays.