[jjtheblunt]

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.

[benreesman]

FWIW I’ve been around for ages and I routinely browse the comments to get signal on whether or not the linked content is worthwhile.

[jjtheblunt]

yep same here: have been here since before it started, and the new person didn't realize such.

[barganzo]

Right, but to not even open the linked page when it is so tiny seems an obvious mistake.