There's nothing on postings since the internet wasn't around then. The manipulations I think the sec is concerned about is when an actual trade takes place. IOW.... if you post crazy things but don't trade, I don't know that you can get into trouble, but I am not sure.
The nasd has rules that cover registered reps. (RR's) My understanding of them is that they (RR's) must notify thier compliance dept. when they post, and the compliance dept must review the postings for approval or disapproval, and keep records. Here's the link to that story: The links on the page need to be read also for a full understanding.