I am greatful for this summary, as I usually check the comments before the link, to see if its worth to click through the cookie consent and Ad spam found on most sites, as well as digging out punchlines from lengthy articles.
I see your account is 1 day old, and your question makes total sense to me too.
So, welcome, glad to have you here of course.
The answer is a commented "tldr" is widely used on news.ycombinator.com, and, as comments below say, it's become a conventional courtesy: people tend to scan comments for tldrs, in order to possibly avoid digressing into commonly (but not always) long winded posts.