This was the reason my company moved to Slack. There's no way for our boss to turn off the ability to read our PMs, so there's no way for us to know he's not.
No one in the company wants this—we expect PMs to be private.
I was concerned too and sent an email to the HipChat team. They responded nearly immediately and updated the original HN post.
To be able to see "private" communications, the manager would have to send an email to hipchat to request certain access. See above for the exact terms.
No one in the company wants this—we expect PMs to be private.