As I said just before that...
My comments about the documentation, here and previously, were referring to the apps schema and not the plugins and I leave them here as evidence of my stupidity
The Obsidian documentation was explicit and I really couldn't understand why you couldn't understand. But that's because you were talking about the plugin, which I'd completely misunderstood. As I said -- evidence of my own stupidity, for which I apologise.
In attempt to make amends, we can now see what's happening. From the KM manual:
Convert Hex to Unicode Characters
Text token fields also process %NN% or %NNNN% or %NNNNNN% as arbitrary hex unicode characters (eg %41% is an A, %01F300% is).
...and, as luck would have it, you've got pairs of double-encoded characters in your URL, eg %252C%2520. KM is spotting the %252C% and treating it as a token -- the Unicode "Box Drawings Light Down and Horizontal" -- and using that in your URL instead.
@mrpasini was bang on the money -- switching to "Process Nothing" stops that from happening. No bugs anywhere (at least, not here!), everything working "as intended".
Thanks both for the fun trip -- I've got a lot from it, and will remember to watch more closely for "inadvertent" tokens from now on.