Ah, I meant forbidding them in the sense that the culture of the organization would discourage people from talking about work related things in a "work context"

Ah, I meant forbidding them in the sense that the culture of the organization would discourage people from talking about work related things in a "work context" via ad-hoc messages, not that people literally or practically wouldn't be allowed to message each other. I agree, that would be draconian.