Thanks - a bit of searching on the OpenSuse site turned up this:
https://forums.opensuse.org/showthre...light=xdg-open
so it's a bug in the xdg-open script when used with XFCE. In particular, it's in libexo 0.10.6 (part of XFCE) and earlier, supposedly fixed in 0.10.7. But OpenSuse has not yet updated to the latest versions.
I was able to fix it by modifying xdg-open to set the desktop environment to Gnome (even though I'm running XFCE . . . .) - then it opens the %-encoded URL's correctly. that fix was from another thread here:
http://unix.stackexchange.com/questi.../170820#170820
Maybe someone else will find this useful :-))