Can a company use private Slack conversations for a lawsuit against you? I work at a company where there's a lot of toxicity and a lot of people seems to be unqualified for their jobs, which leads to a very high turnover. 15 people left over the span of a year. And I did mention to some people that some people seem to be highly unqualified from experience. I am wondering if that can be used against me somehow even if I said what I felt was the absolute truth. I don't think it's necessarily a defamation case, but I don't see what other reason I might get sued for.
Can a company use private Slack conversations for a lawsuit against you?
It depends on whether the circumstances and the parties to the conversation imply that the conversation is covered by something like the attorney-client privilege.
Statements of opinion are not actionable, but false statements of fact are. The terms of your expression(s) are relevant for ascertaining whether the statements are of fact even if framed/disguised as opinion.
If you have evidence that your statements are truthful, the counterparty is unlikely to prevail even if your expressions are statements of fact.
Unless obtained illegally, a private Slack conversation is admissible evidence if it is relevant, in any kind of lawsuit. Even if it is obtained illegally, in a civil case it may still be admissible as evidence and a balancing test between the harm of the illegality and the contribution the evidence would make to discerning the truth of a material issue applies and it isn't automatically inadmissible as evidence.
Whether it would be relevant, and to what, depends upon the nature of the lawsuit and the overall facts.