Hi,
Used /font -z (without any font name, font, size) won't delete "ftreebar" from "mirc.ini". Rest will deleted and we got only: fscripts=Consolas,413,238,0,0,10
Quote from help: "If no font is specified, all windows are set to default font settings."

Regards.
mIRC 7.64 and latest beta.

Thanks for your bug report. That is intentional. The /font -z switch only affects windows. It excludes the treebar, the switchbar, and the script editor, whose settings are preserved.