Let's take it to the outside world, celebrities like DJ Khaled, May weather etc in 2018 was charged for promoting a scam project using their social media platform. These people are influential in the society and can easily be detected if they do anything fishy with their influence on people. In such situation they'll be considered guilty and fined for misleading their followers. Here in the forum, you are not having followers, but people can trust you, therefore trusting any company you promote here too, if need arises for investigation on you for promoting a company, you'll be charged according to what you got paid. Though, it's rare because how would all the participants get charged to pay regarding the difference in locations and identity.
Don't compare yourself to celebrities because laws are different for you and for them. Okay, let the police forces arrest you for possession of hard drugs and then compare yourself to the celebrities who were arrested for the possession of hard drugs. You'll easily end up in jail but celebrities will still be free because it's the fame, status, money that protects them from everything. Imagine Lionel Messi decided to use drugs, do you really believe that any government ever arrest him? Can you imagine what would happen in the world if any police force arrest him?
Wearing the signature on this forum to me looks like wearing a company's t-shirt in public. How can anyone arrest me if I wear some company's logo and url? Even if I print amphetamine logo on my t-shirt and paint a tattoo on my face, I think I'm safe.