[alaaibrahim]

> I can make nasty off-handed comments to my friends in private chat all day, with very little fear that it'll see the light.

And then, someone decides to take a screenshot, out of context, and post it somewhere for the whole world to see.

[problems]

It's possible, but it's far, far less likely than a post on social media with your name tied to it - it's also completely deniable and contains only usernames.

[TeMPOraL]

This crosses the Internet boundary too - see e.g. the well-known case of a guy who lost his job because someone overheard his meatspace conversation and decided to post it on-line...