unfortunately I don't know anything about Philipp Lehmann, too, but I
solved the biblatex-bug I reported in
Since you started an interim biblatex home at GitHub, it probably would
be best to integrate the solution there.
It's basically just a wrong positioned % in the following definition in
There are no spurious blanks anymore in multicite-commands if you
replace the code above by:
Please let me know if/when you include this patch.