I wonder if there have been court cases for this; is slack considered a non-work area for, say, the purposes of discussing unionization? Would a DM between two people mediated through the company slack be a non-work area?

Though generally, it seems this kind of ban (of union discussion or pay) would be unlawful in the US,

> For example, your employer cannot prohibit you from talking about the union during working time if it permits you to talk about other non-work-related matters during working time.

https://www.nlrb.gov/about-nlrb/rights-we-protect/the-law/em...