My short-term memory ain't that good, so I didn't harken back to those two posts.
I don’t know how, but I found that Keyboard Viewer (tiny, barely readable panel) and somehow got it installed in the menu bar. It does what you said, but it’s not as useful as KeyFinder which explicitly defines the keystrokes for particular characters.

And then I came across a panel which is titled Characters showing various things and notes that one can “Add to Favorites”. What does that mean? And how would one use it? What are Favorites and how do they relate to working with a keyboard and writing stuff down? This is all massively confusing.

And yes, it is "a description of what you found in Console > /private/var/log > fax" (ie, of no value).
As for the URL: I don't know which one you're referring to, but I certainly read at one point or another.