I've encountered an issue with the Face to Face mod form, whereby, multiple email addresses are being stripped from the "Third-party email address(es)" field. Specifically, whenever I enter firstname.lastname@example.org,email@example.com and click the save button the data is not saved.
I've had a look at the PHP code and I believe the issue arises because the $paramtype value for $mform->setType is PARAM_EMAIL but that validates single email addresses only.
Line 57: $mform->setType('thirdparty', PARAM_EMAIL);
Change PARAM_EMAIL to PARAM_NOTAGS