> you mean they can potentially sell my personal conversation with a friend as if its a company owned data

Don't do it on company slack then?

Whether or not this news is a surprise to you, you must already be separating concerns. At most competently run places emails/chat logs etc are logged.

Assuming you and your friend both work at the same company using the same Slack Workspace and someone would be willing to pay for the data? Yes, it is a possible scenario. I have no idea why a company would offer to sell it's employee chat logs but I am sure there's a more clever individual out there who can think of reasons.