There's no official guideline (we try to keep that list minimal), but I think it's harmless and the main thing commenters should do is not complain about it. These complaints are always the same, always offtopic, and usually balloon in size to the point where the offtopicness drowns everything else. That's a terrible outcome for a thread like this.
Even if you dislike "I'm $X years old and I $Y" posts, it's not helpful to give a kid a grumpy patronizing response. We want HN to be a helpful community, not some weird age competition.
Even if you dislike "I'm $X years old and I $Y" posts, it's not helpful to give a kid a grumpy patronizing response. We want HN to be a helpful community, not some weird age competition.