The old "file has been modified" problem...

Log in with two different users who are able to approve/disapprove posts.
Enter MCP, select one post waiting for approval (with both users).
1st user: Approve post -> post gets approved and is viewable.
Then disapprove the post on the other user's MCP -> post is gone...

Should probably check if the post is approved/disapproved already and if possible ask what to do, maybe:
[list: bbbc3]

• case 1:
  "This post has already been approved."
• case 2:
  "This post has already been approved and therefore cannot be disapproved any longer.
  Do you instead want to delete it?"
• case 3:
  "This post has already been disapproved."
• case 4:
  "This post has already been disapproved and therefore cannot be approved any longer."

If you offer the possibility to delete the post (case 2), it would be possible though to remove a post which has already been answered after the first moderator approved it. Not that good...
Maybe a warning? "Do you instead want to delete it? (Be careful not to remove a post out of context by accident)." Or simply don't offer the deletion possibility...

((Another possibility (referring to simultaneous editing in general again): "lock" the post in MCP until the first user has completed his/her actions on it, but then there's the problem of browsers "back" button, i.e. not "unlocking" posts and so on... So the method above would be better probably...))

...and no, it's not "unlikely to happen", I can imagine at least one situation where it's very likely to happen - even at a small forum/board...

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...aargh even lists have space after them, not only quotes