Sure, it's OK, so perhaps I should be grovelling for messing up again!
What I did was to change the permissions so you had to assign the moderator to a special member group to allow them to post polls in announcement boards, whereas you've automatically given them that right if they're a moderator for that board (which is probably tidier in most circumstances).
!in_array($username, $moderators) denies the necessary permission if the user isn't a moderator for that board, so it's absolutely sound unless (for some strange reason concocted solely to justify my original solution), you want to appoint more than one moderator to that board but specify which of them can or can't start polls!
