http://boards.straightdope.com/sdmb/showthread.php?s=&postid=2947972#post2947972
Above is the longest post I have ever seen on these boards (quite appropriate too). I was wondering if there exists an even longer one, out of curiousity.
Heh heh… Lib’s got a long post.
I’m sure there’ve been ones with more content, but scroll-wise, that could be it. I remember someone mentioning how they were proud when they get a “Post too long” error when trying to post, so there seems to be an upper limit.
The maximum permitted length for a post is 20,000 characters - there is a link called “check message length” at the bottom of a reply box (not the quick reply at the bottom of the thread, but the one you get if you hit the “Post Reply” button) that will count the number of characters for you and tells you of the maximum.
Lib’s post was only 6760 characters, so I am sure there must be longer ones - the search is on… 
Grim
The OP in the GQ sticky thread is 11785 characters long. Maybe that violates the spirit of Joe K’s question, though, because a lot of that length is in the URL coding. I happened to think of this post because I’ve got an updated version of the same ref list that runs to ~20200 characters
As a former EMT, I very well recall Cartooniverse’s Everything’s Changed post (about his experiences as an EMT in downtown Manhattan Sept. 11-13, 2001), which, with spaces, has 36648 characters (and no URL coding).
Zev Steinhardt
Nah, that’s fine, I should have been more explicit in saying that I meant the length in scroll length. I kept scrolling Lib’s post and scrolling and scrolling…
By far the longest one I remember scrollwise was back with the old software. The administration had experimented with making available the “members” feature which gives posting stats on everyone. Because of the crippling demand it put on the hamsters (who nearly died of heart attacks) it only lasted a day or 2, but one poster, I forget who, was able to copy and paste the whole list into a thread before the feature was disabled.
Find that thread, and you have your OP answer.
There was this thread where I asked for a list of all the legal Scrabble words that ended with A and Satan responded by posting all 2880 words (in a truly long post, list since snipped by manhattan.) And, since I was still a young and new Doper back then, and didn’t know any better, I responded by hitting the quote button and copying the entire list.
Zev Steinhardt
You know, I thought briefly about doing that with Lib’s post for giggles, but immediately thought against it. That would be jerklike.
Heh, I just read that Scrabble thread, and Wally said that he misspelled one of the words. 
Thanks, all, for the answers so far.
well, I tried to find it but alas could not. Perhaps I shall try again tomorrow.
Okay, here’s the winner and runner up (not sure which is which though):
http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=78920
http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=29678
Thank you! 