Good question. Ethics would suggest that crowdfunders should probably voluntarily disclose any conflicting interests in a company that may bias their review. In practice, nobody really does unless you’re legally compelled to (which I don’t know if Trustpilot do) but they certainly don’t put any prominent disclaimers to say you should.
The cost of policing this anyway wouldn’t be worth it and if it’s tucked away in T&Cs more fool them. Investors hold such small %s that it’s effectively immaterial on an individual basis I would have thought.
Also, all these platforms know that companies with engaged investors/followings exist and it’s just par for the course really.
If you find anything in their T&Cs, I’d be interested to see it