I added DIR attribute in my ics file for an event with the ORGANIZER property. My code is like
ORGANIZER;DIR="ldap://example.com:6666/o=ABC%20Industries,c=US???(cn=Jim%20Dolittle)":mailto:[email protected]
But i don't know where it is actually used or how it will be shown to my invitee.
iCalendar has LOTS of features. Clients that use iCalendar don't need to implement or use all the features. So if it's shown to an invitee is completely dependent on the client which you are using.