An interesting phenomenon.
Can anybody reproduce this?
Click on any pre-existing favorite to visit the site (note the address in the tooltip) - screenshot taken before site loaded:

The site has now loaded.

Now click on any link on that page that takes you to a different URL on that same site - I chose one to take me to information about Port 6000... but look what has happened to my favorite - the URL has changed!!! (check out the tooltip - the Favorites URL now matches the new page being viewed). Yes, if I click on the Favorite now or checks its properties, it confirms the Favorites URL really has been changed 

I try another hyperlink on that page.. it happens again...

And again...

This is happening with every Favorite that I have tested so far - it is possible that my favorites folder or its contents have corrupted (despite this laptop having been reformatted only a couple of weeks ago), or that the favorites archive that I exported before reformatting, and later imported into this clean install, was corrupted somehow, and I'm still trying to work out how to reliably rule out that possibility. I'll be interested in hearing if anybody can reproduce the problem.