A submission to HN (https://news.ycombinator.com/submit) has three fields: title, url, and text. The submission form says, "If there is a url, text is optional," and indeed most submissions with a url provide no text. This standard practice means that HN readers have only the submission title and url as clues to what the submission is about.
Submission titles are necessarily brief, not only on the author's side but on the HN side, whose title field has a limit of 80 characters. Some article titles are clickbait, and others are too clever for their own good, but even if the author is trying hard to accurately portray the content of the article, there's only so much you can say in a title.
The result of this situation is that HN readers end up clicking on articles that they would not be interested in reading if they knew what the articles were about, and they avoid clicking on articles that they would be interested in reading. As a workaround, some HN readers just go straight to the comments to see whether the article is worth reading. However, the comments tend to be hit or miss, ironically for that very same reason: a lot of readers are going straight to the comments without reading the article, so there's a kind of tragedy of the commons where a large % of the commenters are ignorant about the article. Moreover, even for commenters who have read the article, casually dismissive comments can rise to the top, upvoted by readers who haven't read the article.
What I'm suggesting, then, is that as a matter of standard practice, it could be very useful for article submitters to summarize the article in the submission text. Presumably the person who submits and article has read the article and is not dismissive of it, considers the article worth submitting. And if the submitter has not read the article before submitting, the absence of a summary would be at least a semi-reliable indicator of that fact.
I think it would be interesting to have expanded HN submission lists that include summaries inline, perhaps with the summaries limited to a certain number of characters.