I have no problem with this. I worked at a company about five years ago where employees used G chat to say some really nasty things about other employees. I only found out because one of them was using a temporary laptop that we had to do presentations, and I opened it up and G chat loaded and there was this disgusting talk about other employees trashing them, talking about the religion, all of this stuff. People ven…
Certainly company tools are under company control. Yet in the age of the pandemic consider that the bar isn't an option. One could start a Signal conversation or group, but it's higher effort. Of course there are some lines we shouldn't cross, even if just venting. Hopefully we can all learn to be more gracious and humble, while maintaining a healthy amount of candor.
If you want an OTR conversation then do it in person (though they might record it on their phone or take a contemporaneous memo, a la Trump Whitehouse), or in Signals with expiring messages (though even then you might need to assume the other party is screen capping the messages).
So best of all is to assume your messages/chats will be leaked selectively. Avoid gossip and innuendo!