Can’t anyone already do that with a screenshot or a log dump? I’m always assuming company provided comms platforms are fully readable by the admins

If you wrote it on your company's slack space, it is not really private to the company. Everytime I have a "private" conversation in Slack I have the understanding that the information could be shared. Even now there is a share button not for the whole conversation but yes for individual messages

Every thread participant should check [_] I agree before the thread is published.

An inappropriate message may not be about something unsavory but about something private. Information about a contract which is not yet public. A discussion of a candidate who is then hired, and reads it. Etc.

Who would put a career ruining message on slack or any other company platform/service?

Your Slack admin can read all messages regardless of where it was posted via SIEM

1. A workspace admin or 2. by permission of all on thread, or AI inspects contents and gates on 1 or 2 if anything sensitive. This isn't 1990, we can program stuff now.

The only actually interesting thing about this regarding "career ruining messages" is how easy accidental disclosure violations would become.

That can already happen with screenshots

Publishing "career ruining " messages on a company managed chat app is probably a bad idea in general.