Not clear from your reply whether you added it (as a mod) or you are announcing to the gp that the year has since been added as at the time of your comment (i.e. by the poster or a mod).

Yes

> as a mod

I consider adding a year to a post to be more of a janitorial service than moderation, similarly how some users can flag comments. But of course you can call it whatever you'd like

In a way, that makes you a mod even if you don't agree with the moniker.

I can't find the specific dang comment out of the zillions but you can just email hn@ycombinator.com if you are lusting after the power to fix the years in titles.