I asked how it's legal and you answered that it's anonymous, so I'm questioning how that matters since if it's illegal they can just track them down - for example by subpoenaing the IP address and then searching the computer itself and cross referencing the suspected parties to the list of people who traded and profited from the stock.
The only issue would be if someone that's licensed and regulated would do something like this, which is where the anonymity comes into play. But if it's posted as an opinion rather than a recommendation, it might not even be worth the effort on the chance that it might be a licensed person.