Should not be able to set resolution as 'Duplicate Issue' without stating which issue it is duplicating.

Currently when resolving an issue you can select the resolution to be 'Duplicate Issue'. This is helpful, but what someone interested in this issue, say JB-2, really wants to know, is which issue the closer thinks this one duplicates, say JB-1. Not specifying the id of the duplicated issue, JB-1 here, adds additional communication overhead as anyone reviewing JB-2 must either review associated documentation to see if anything is mentioned or contact the closer directly to determine what they were thinking at the time they closed the issue.

The work around at the moment is that you can enter a JIRA id in the comments field, but this is not mandatory. JIRA should be updated to require a 'Duplicate JIRA ID' field to be filled out when resolving an issue and marking it as a 'Duplicate Issue'.