It comes down to whether or not it is considered material and misleading. If it is material and misleading, then it is fraud. If not, it is free speech. There are various related laws. Here is one relevant law:
"
to obtain, by means of false or fraudulent pretenses, representations, or promises,
any money or property
in connection with the purchase or sale of any commodity for future delivery, or any option on a commodity for future delivery, or
any security"
What is fraudulent?
"To make any untrue statement of a
material fact or to omit to state a
material fact necessary in order to make the statements made, in the light of the circumstances under which they were made, not misleading"
So, it comes down to whether or not the statements that the stock was "going to the moon" or similar statements were material. That goes beyond my knowledge of laws. But to me, it seems material.
The rest is under conspiracy laws (18 U.S. Code § 371). Did they agree to spread the information? Did they willfully spread the information? Did they act on that agreement? Answer no to any of those, and it is okay. Answer yes to all and it is illegal.
I personally think the posts on WSB seem to be agreements, were willful, and were acted upon. But again, that is beyond my knowledge of the law.