The Share button is currently used to send notifications to reviewers that have not yet completed their review when the review is not overdue, as described at https://confluence.atlassian.com/display/CRUCIBLE/Using+Review+Reminders. The term is quite confuse, as it seems this button would serve to share the review with people that is not a participant.

The suggestion is to change the text of the button to Send Reminder, as this is actually its purpose.