> "Feudalisms" were diverse.
>
For what it's worth, "feudalism" is mostly a dirty word among medievalists, these days. This is not my specialty, but there are multiple problems, probably the most serious being that the term implies, as you suggest, a non-existent uniformity (and rigidity/stability) of practice across Europe "during the 'feudal' period" (whenever that was). I certainly can't speak for Medievalists, but in general I think you will find that medievalists will say the word doesn't mean very much, and they tend to avoid it. If you want to troll a medievalist list, ask them about feudalism.