2019
1) Someone may have read the essay before, remembered the point, but forgotten the exact title. It has, after all, been posted on HN twice before. Simply reading the comment that it's from 4 years ago may be enough to confirm that it's the same article, as it did with me.
While the essay has the date right at the top, in general there is no consistency about where people post a date, or if there is one at all.
I know that I sometimes skim the HN comments first rather than follow a page link because then I don't need to worry about cookie notices, requests to subscribe to a newsletter, etc. This essay does not have those, but enough do that it's a general nuisance.
2) Software changes over time. Cap'n Proto's Schema language may have changed since then - perhaps as a response to this essay - making this essay of historic interest only. While that is not likely the case, it is an example of how having the date may provide helpful information.
This is useful enough that it is accepted practice to add the date to older information. For example, the previous two HN submissions to this essay both include (2019) in the title. See https://news.ycombinator.com/from?site=zenhack.net
because it's so difficult to find the date of publication before people waste their precious time goofing off from their overpaid jobs.
You can see dang, one of the moderators, write: "It's the convention on HN to add the year to a title when the article isn't from this year." at https://news.ycombinator.com/item?id=27867435 ,
write "On HN, it's the convention to add the year when a story is more than a year and a bit old." at https://news.ycombinator.com/item?id=16306830
and write "It's just the convention to add the year in parens (and for commenters to mention when we missed one)." at https://news.ycombinator.com/item?id=8244765 .
Found via https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que... .
If orhmeh09 has issue with how to interpret the submission guidelines, I suggest contacting hn@ycombinator.com to resolve the issue.
In retrospect, my original comment was probably too terse. It's not obvious if I was suggesting that "(2019)" be added to the title, or if I was claiming that the article was outdated for some reason. That's my fault.
Honestly I didn't expect my original comment to be controversial.
See dang, one of the moderators, affirm this multiple times at https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que... , most recently 17 days ago.
Since moderators have promoted this practice for at least a decade, it's much more likely your interpretation of the guidelines which is wrong.
Any moderately good rules lawyer would point out the guideline is "please use the original title" not "please use only the original title" nor the even stronger "use only the original title", which turns the polite request into a requirement.
Adding the year is not editorializing. Nor is adding "[video]" or "[pdf]", nor even adding the conference name and year as https://news.ycombinator.com/item?id=37216895 did 11 hours ago.
Since there appears to be a conflict between your understanding of the guidelines and that of the moderators, you should take it up with them at hn@ycombinator.com in hopes of resolving the issue.
After all, the guidelines say "If you're worried about abuse, email hn@ycombinator.com and we'll look at the data." ;)