I am not surprised to hear about the bold part, but question whether or not this is legal on an employer's part. Employers can (and should) censor employee communication regarding their specific industry (customers, competitors, etc). But they can not censor employee's speech in general. Obviously there are gray areas on where you draw the line and my understanding is from a legal sense the line fairly well defined to a specific & narrow set of firms that an employer interacts with or competes with. Having an investor with an unrelated investment does not qualify.

A bitcoin company does not work with or compete with an altcoin company, they are in separate areas. I would not be happy with an employer who censored me here, and think I would have legal standing to push back on that.