Okay, here's what Ancestor and I have found:
1. I submitted the requested edited bookmarks.html file to him. For reasons unknown (and likely unknowable), all the entries in that file worked for Ancestor, but not for me.
2. I then did some experimenting and discovered that, were I to remove and replace the bookmarks.html file entries that would not show in Brief for me, these feeds then worked correctly.
(Now to figure out how to make the newly-entered feeds appear in alphabetic order in Brief; they are correct in the .html file, but in Brief they appear in the order in which I entered them, below the previously-working/not-removed entries.)
Thanks to John's help I finally managed to figure it out. It turns out that Brief wasn't showing some of the bookmarked feeds because they waren't Live Bookmarks. Instead, these were just feeds' addresses saved as ordinary bookmarks. They may be easy to confuse, so anyone is experiencing this, please make sure that your feeds are bookmarked as Live Bookmarks.
John Liebson wrote:Now that I have Brief working (that is, showing all my news feeds,) I have found a problem:
I use TabMixPlus. When I middle-click on an entry in Brief, the article opens in a new tab, as I expect. What I don't expect nor like is that Brief resets itself to the top of its feed page. That means that I then have to scroll down through Brief again to find where I was when I middle-clicked to load an article in a new tab. Brief ought not do that; it should stay where it was when I middle-click to load an article.
Or, as we all say, on a daily basis in Latin, in medias res, which, mistranslated, reads, "Kindly stay where you were...".
This happens when showing only unread entries, doesn't it? It's a known issue, unrelated to Tab Mix Plus, and I am planning to fix it.