I am unable to do /is trust as I am not the leader of the island even though I have permissions to /is invite a person to the island, build, break, open chests, etc. (I am the member) Im suggesting to enable /is trust and /is untrust so that we are able to make trades with other people when the owner of the island is offline from the server
It looks like that is by design per the author of the plugin. Let's gauge interest and go from there.
The trust feature is custom made and not part of the skyblock plugin. It doesn't know much. I think it is checking the worldguard region for the owner to see if it is allowed.