An addition to the post size limit issue: the fanfic section has a stickied index thread, which serves as an index to the fic that has been posted there. It goes back for years, and is a very valuable resource. If the post size limit remains in place, that might be jeopardized, as all that link code does eat up characters, even though they are not visible on the screen.
Seriously, has there ever been a problem with people posting too-long posts? Not to my knowledge, though admittedly I've only been here a little over a year. Is the limit a problem? Yep, in the fanfic forum it definitely is. If a compromise need be made, how about extending or removing the limit in that forum only, as that's where the big long posts will be?