There are always issues with the quality of stats and methodology when using postings/threads for this purpose.
One issue is how many forums do you include? Does some of the bickering on hotcopper count? If you look at the two threads compared, MUL and ZFX, do we look at the number of posters (for eg Chicken has posted almost all the posts on ZFX; MUL had Stefan posting prominently but now he's away for a bit, so do we then consider the posts of certain posters with a greater weight? Does the absence of a prominent poster affect things? ie do we look at the profile of posters?).
Also the issue of entry, some people may have been on a stock for awhile and then post on it to push it a bit higher before it slows, how do we pick rampers? Also don't forget that we don't really know about the volume of posts on a stock till AFTER the posts build up so we may have missed the bulk of the move. With cases like MUL the sheer volume of posts may not be conclusive as you pointed out. There are some threads which have looked promising but have died with the stock after an initial flurry of posts- it that sense would we get more info off the price chart or anncts than the threads?
If we are looking at posts for an indication of crowd interest or behaviour wouldn't existing indicators be sufficient?
Rather than trying to throw cold water on the idea I'm trying to point out how difficult it may be to come up with a system that can be applied consistently, with defined parameters- perhaps that is something we can continue to discuss. My primary concern is that another indicator is just going to be a distraction, I have trouble enough with the current ones!