I don't think anyone but the institutions realistically can or should be able to be charged. Fraud requires reliance on the information. No one on social media was selling a product, and there was a very clear intent amongst many that while it may have been intended to hurt hedge funds, it was all about taking the stand.
That's speech. WSB is not your or anyone's agent in the long run. Now I'd like to know who was funding the Silver thing. If that can be traced back to a hedge fund or financial institution who should all know better than to do something like that, then you may have got a case.
If it was just the media and a woeful lapse in journalistic integrity... Well... Back to speech again.