Dear Oliver
I am no expert, but after your first email, I played around a bit. I am on Ubuntu 18.10 running Pd 0.48.2, and I cannot reproduce your problem. I tried:
pd -font-face "Celeste Small"
hi, a small update !
your method actually works when i call PD from the command line like you suggested.
but when i write the -font-face flag with a font containing spaces into File/Preferences/Startup ... the formerly described errors occur
so, ".pdsettings" must be the bad guy here ...
anyway: thanks for leading me on the right track !
enjoying my courier ! ;-)
best
oliver