Becky suggested a confidential tag for Discourse a while back (you can find the thread here), and the Discourse people said they planned to add something like that called a “whisper”.
This thread also on the Discourse meta posted a bug report saying that replies to whispers should also be whispers, implying that whispers were already implemented. Assuming they’re implemented, how do we whisper?
That feature is still in development. You can find the option to “enable whispers” in Settings --> Basic setup (or just use the filter), but there’s still some essential UI missing before it’s really user friendly.
Keep an eye on that topic you linked to for updates. (thanks for the nifty custom avatar btw!)