I like it as a clear visual indication of where the URL ends. And a page often consists of more than just one file (images etc.) (the HTML portion of the page is just an implicit index.html in the directory), so it does make some sense.
But is an article an index to the attached media? Not even "just", but "at all"? Is this the right abstraction? Or do we have a better one, achievable by simply removing the trailing slash?
We discuss this in the context of cruft, user friendliness, and selecting proper forms of expression, which the original article seems to be all about, by the way.
My point is that “an article” generally doesn’t consist of just a single file. Or maybe rather, that the distinction between a file or document and a folder isn’t necessarily meaningful. Physical “files” (i.e. on paper, as in a filing cabinet) actually commonly used to be folders. And there is little difference between a zip file (which are used for a number of popular document formats) and the unzipped directory it contains.
Unlike in file systems, we don’t have the directory–file distinction on the web, from the user perspective. Everything shown in the browser window is a page. We might as well end them with a slash. If anything, there is a page–file distinction (page display in the browser vs. file download). I agree that URLs for single-file downloads (PDFs, images, whatever) should not have a trailing slash.
