Maybe a court would decide that heart emojis aren't a company secret covered by an NDA, but are expression of solidarity with workers which is legally protected speech regardless of what the employer thinks about it. Or maybe not. By the free speech ideology you can't know, and are supposed to assume innocent until proven guilty, and keep it until a court orders taking it down.

But here a private company is executing its own unilateral judgement by their own clearly biased moderators.