>>andsoi+S6
this is a sword that cuts both ways though. in my experience, employers are much more interested in minimizing the attack surface for subpoenas than jamming up employees for indiscretions that took place over company comms. companies I've worked for have retained emails and chat logs for the minimum duration required by law and aggressively purged anything falling outside that window.
as always, you do need to be careful with written communications, but I highly doubt companies are recording slack huddles of rank-and-file employees. it's expensive and creates unnecessary risk. there's no real reason to do so when the alternative is, at worst, paying 6-12 months salary while the unwanted employee is managed out.