> You turned it sideways. Using a colon, a dash, and a parenthesis character in series, you could make a sideways smile or frown. It looked like this: [happy-face] or [sad-face]

Did the editor repace :) with [happy-face]?

??? This isn’t on the linked page.

Wrong thread. The correct one is https://news.ycombinator.com/item?id=49767371

How does that even happen? HN software hiccup? Or what?

Probably my bad.

I guess:

Click on the HN discussion > Click on the article > Notice the weird CMS error > Copy the sentense > Click back > Click back again by mistake(?) > Click on the discussion of the wrong article (?) > Paste the sentence > Notice that HN eat the emoji > Add the version in brackets.

Maybe the author uses a CMS that's supposed to replace tags like [happy-face] with an emoji, but something broke?