Maybe leave a breadcrumb behind for 1-3 weeks.
Where the old thread was, leave a placeholder thread with the old title and just one post:
"This interesting thread was moved to <<LINK>> to increase its visibility to members of other forums."
Or leave the old title in the old forums' list-of-threads, but clicking on it takes you to the new forum.
I agree it's a tradeoff.
Is there any way to monitor what % of active members regularly check the "Ask A Question" forum, or the "All Things" forum? My guess would be that no more than 5-15% of those who regularly watch several topic-forums regularly check the forums where new members mostly post questions.
And I've become slower to "poke" people using the "@name" method. While it's true "they can always just not respond", I'm from New Jersey, so concepts like "polite" and "pushy" are hard for me to keep separate. They both begin with "P".
