It doesn't emphasize the metadata over the content - they are equal peers.
Most techniques for making metadata less emphasized make the metadata objectively less readable. I like having the metadata there. I like being able to read it. I have no trouble reading the text (because it's a decent size and the layout handles zooming without issue.)
It puts the metadata first with no visual distinction from the content itself. The distance between paragraphs in the comment and between the metadata and the comment is identical.
Also, the title of the article is repeated throughout and drastically emphasised (considering nothing else is that visually distinct and it even has a solid background color).
The typical LWN reader is a heavy mailing list consumer. Emails have subject lines so having subject lines for comments is very familiar. Many people take the default subject heading because they are making an on-topic comment. I think outsiders aren't used to seeing so many on-topic comments so it throws them off.
Using a line break between meta data and content is also a familiar paradigm. Spend 20 years reading your email with mutt or mailx and you'll catch on. ;)
Most techniques for making metadata less emphasized make the metadata objectively less readable. I like having the metadata there. I like being able to read it. I have no trouble reading the text (because it's a decent size and the layout handles zooming without issue.)