Why do you
let him derail the thread?

Fair point. Normally I just hit the report to moderator link and write
'off-topic'.
I have seen grue and SaltySpitoon to be inactive for more than a while now(inactive as in spending less time on the forum, moderating). So the absence hasn't affected the spam to increase. Although, I could argue that with the launch of the new autoreply bot,which might have made the spam problem much worse than it already is.
Yeah, it could be something else like that. I do get feeling that 3 global moderators aren't enough given the level of spam this forum is subjected to.