I also have a delay set in my profile. I give myself 10 minutes to edit or cool off and delete. But I have never seen a [delayed] comment. That seems to undermine the purpose of the delay.
It could be a bug. If the comment is about to become visible the code that chooses whether to show it at all might think the delay has expired but the code that renders it might still think it should be delayed. Especially if the rendering happens first.
Maybe the person who saw it as [delayed] is using a third party HN reader app and the HN website itself filters out delayed comments while returning it via the API as the [delayed] string and expecting clients to do the filtering?
I've been an active reader on HN for over 12 years and I have _never_ seen a comment displayed as [delayed] even once. Not on the site nor any of the third party mobile apps, and I've tried a lot of them. Weird.
It's a little more complicated than that. A long time ago delayed comments actually showed up in the API, leaking their contents early. I reported this to 'dang as it obviously broke the purpose of the feature, and at some point the behavior changed to returning "[delayed]" for a bit instead of the actually contents of the comment. I assume changing things to indicate that the comment wasn't available yet was more work, and this was an easy compromise.
