One-paragraph entries use their entry in the archive as a permanent link. This is because the first paragraph is displayed there; if there's only one paragraph then that's the entirety of the entry.
But if I update a one-paragraph entry, especially significantly, its permanent link should be its own page. For this reason, and for the craic, every entry will now have its own page. My apologies for duplicated items in the Atom feed.
Note that the “old” links haven't been broken - they still lead to the archive.