For collection WebDAV accounts make “Server handles meeting invitations” read-only setting
Just like user cannot change the URL of a Task/Memo/Calendar/Address list, that was discovered over WebDAV as part of a collection account, users shall not be able to change the “Server handles meeting invitations” bit.
With other words, if the user removes the bit, the server will continue to handle meeting invitations and if the user set the bit for a server that does not send invitations, the change will only cause confusion. There is no use case, where the user shall change the “Server handles meeting invitations” for a WebDAV-discovered calendar/task list.