Yup, it is here :
ls -ld ~/.config :
rwx------ 17 simon simon 4096 sept. 20 21:29 /home/simon/.config
ls -ld ~/.config/mopidy:
drwxr-xr-x 2 root root 4096 sept. 20 17:42 /home/simon/.config/mopidy
ls -l ~/.config/mopidy/mopidy.conf:
-rw-r----- 1 root root 84 sept. 20 18:57 /home/simon/.config/mopidy/mopidy.conf
cat ~/.config/mopidy/mopidy.conf
[mpd]
hostname = 192.168.0.19
[spotify]
username = thesimeox
password = *password*