If you try to comment lines with Ctrl+E in a Fortran90 file, "c" character is printed. However, the comment character for free format fortran file is "!". The bug is located in filetypes.fortran, line 37 (see attached file).
> geany -d :
Geany 0.15, GTK+ 2.8.11, GLib 2.8.6
> system :
SUSE Linux Enterprise Server 10