When adding an event with following alarm spec. in iRony:
BEGIN:VALARM ACTION:DISPLAY TRIGGER;VALUE=DURATION:PT0S DESCRIPTION:Default Mozilla Description END:VALARM
it is then converted to:
BEGIN:VALARM ACTION:DISPLAY TRIGGER;VALUE=DATE-TIME:19700101T000000Z END:VALARM
Which means that alarm description is lost and the trigger is wrong.
Another story is if such alarms are handled/displayed correctly by other clients e.g. Roundcube. I'm afraid they might be handled as no-alarm.