A good lawyer can argue that these people are exercising their first amendment right of free speech. They are not reporting false data and most of these people commenting have "average" net worth not millions/billions.
Its also very hard to prove to a jury that a message from such an average joe on a message board is enough to form a "scheme" with million other readers on wsb.
And, anyone who bought shares or told someone to buy shares with the intent of driving up the price also did something illegal - but it's something that is done constantly and considered a fundamental part of the market, either as an attack on a company in the classic hedge fund short->bankruptcy or, more benignly, like buying up shares of a takeover target slowly so people don't notice you are interested and buy it, which would raise the price.
That gets posted to remind people that WSB is a bunch of random people on the internet. They have no duty to anyone.
Anyone who told others to buy and hold with promises of short covering and higher prices is party to market manipulation, and it is absolutely, definitely illegal. Whether they'll be able to unmask and charge people behind the anonymity of WSB is another question though.