2006 is very impressive! When did the forum start?
Anyways, Introducing Ourselves has 1179 posts, which gives it ~.2 posts/day, making an extremely venerable but relaxed thread. Looking at Top => All Time, a promising candidate seems to be the Inform 7 open-source thread, which has 287 posts from April 28 to Sep 6, giving it, (using ~5 months as the time estimation) ~2 posts/day.
This thread, IFC entries get drawn, starts on the 1st of October and ends on the 31st with 129 posts, doing the best out of the above at ~4.2 posts/day!
Actually, I’m a little surprised, the Top tab doesn’t seem to be reflecting absolute replies, absolute views, or replies over time - it’s pretty opaque. I wonder how it’s calculated?
For example, my Top → All Time tab looks like this when I search for the positive/neutral thing thread:
which doesn’t really seem to clearly be doing views or replies.