J-Pilot is using css rather than rc files since version 2.
If you copy /usr/share/jpilot/jpilotcss.default to ~/.jpilot, it will use that file, and you should be able to tweak the settings. I thought it was installing already to the home directory, but I missed something.
At the bottom of the file there is the following lines:
* {
font-family: Arial Black, sans-serif;
font-size: 10pt;
}
Change "font-family: Arial Black, sans-serif;" to "font-family: Arial, sans-serif;", and the font won't appear to be bolded everywhere.