Found it! Thread started on March 21, 2001:
http://boards.straightdope.com/sdmb/showthread.php?threadid=64354
Actually, rereading it, maybe the thread itself is not so weird. Yes, the subject matter is a little disturbing, but in the best tradition of the SDMB, there is a serious discussion about apotemnophilia (the desire to be an amputee), and also some discussion about it possibly being a hoax perpetrated by a guy who had a thing for women who were amputees. An interesting look back, anyway.
That would be this lovely thread…
http://boards.straightdope.com/sdmb/showthread.php?p=8439279
and the related Pit thread…
Wherein MizGrand proceeded to crow about her affair with her local cop that her dimwitted husband would never find out about. She was chewed for her callous remarks and soon resorted to shouting “You just don’t understand!” into the ether.
Eventually it came out that she had posted a ton of personal information to the board and that her husband would likely put the pieces together soon.
Oh yeah. That was about the maddest I’ve ever been on these boards (I even ended up Pitting her, too, for the bullshit name change, in my one and only Pit thread of another poster).
Seriously, dude, trying way too hard.
This has always freaked me out. Anyone got a link?
Thanks! No matter what I do, it always takes me to only threads within the last two years, even when I select “any date”–what’s up with that?
I think the weirdest part was the capital letters for the “DORRNANCE #5…” and so on–I always imagine someone saying that in a really low pitched guttural voice. Ugh!
Anybody remember Roland Deschaine? He started a thread about swingers clubs for advice and ended up revealing that he first hooked up with his wife because he slept around a lot and ended up getting attached to her but admitted to being a sociopath, emotionally abusing her, said he’d threaten her with death if she tried to leave…and then got pissy in a pit thread when people talked about how his wife should RUN RUN RUN. (And brought up a lot of TMI like how he hated the smell of shit emanating from his John Thomas after anal.)
What are you looking at me for? I posted in that thread with impunity!
I think the weirdest thing I ever saw on the dope was the thread about all men assumed to be child molesters and Scylla posting some very very disturbing stuff regarding his views towards his daughter, how he basically owned her and she was his territory and anyone looking at her was threatening what was “his”. Oh, and how 7 year olds are sexual predators.
I don’t think I’ve ever seen a thread take such a violent turn at the intersection of wrongness and disturbing.
I was thinking it, but yours involved watching piss run down sinners legs, right?
Not in the same categories as some of the weird mentioned here, but all this talk of prehensile foreskins makes me remember the prehensile rectum. The OP was pretty great (and the poster making the post was sane. Just with insane co-workers.), then we got a post in the spirit of Dr. Seuss!.
For another compilation of great SDMB threads check out this thread, too.
I agree that we need to find a link to this thread.
I seem to recall that later on he wondered why people were a little creeped out by him.
I really, REALLY wish Homer would come back. I miss him. 
IIRC, then MizGrand changed her name, thinking it would make her anonymous-only she was too stupid to realize it would change all of her previous posts as well.
How about the guy who liked the smell of his own farts?
From one of our FAVORITE trolls (he’s banned, so I assume it’s save to refer to him as such):
Vaginal lubrication in prepubescent girls
I slightly remember one about someone who was trying to get rid of gophers, and was basically getting really angry with them? It was meant to be funny, though, so may not fit in here so well.
I bring you the interesting mind of a poster called Question. This ( http://boards.straightdope.com/sdmb/showthread.php?p=4411166 )thread is an example and contains such gems as:
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so, since reality is unaffacted by time the only thing that prevents us from understanding existance in totality is our attachment to the perception of ourselves as something different from the energy that forms us and everything else. the past only exists because our minds are finely tuned machines that filter all of reality that has ever existed so that we can understand it based on who we are now. drugs, sleep, divine influence and many other things can interfere with this process and allow some information through that isn’t totally relevent to our current incarnation but is nontheless related, past lives included.
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our subconscious that exists in a quantum state analyzes the information and transmits it to the rest of the brain, triggering whatever process that alters the shape of our synapses to form long term memories."*
That was a Scylla thread.
Well, only a subset IIRC - those sinners who liked to blow hard about how if there WAS a God and they ever MET him, then by gosh and by golly they were going to kick him inna fork. :rolleyes:
And the good Friar did opine that after the celestial pantmessing it would all end in tears, contrition, and forgiveness.
Hallucinating Homer is one of my favourite threads so far! 
This one was pretty wild:
Some 13 year old blabbers on about the whole world is full of pain and suffering and that the universe would be better off if all of humanity agreed to stop making babies so the human race would all go extinct.
Oh man, I missed that one.
This is the best part:
Hello!
This thread (the one you’re reading!) made me de-lurk and become a member.
So it’s all your fault!!!
Hunh. Not so secret any longer, my Panda friend.