Ticket Linking
I would also like to have the ability to "link" tickets together, rather than merging them.
1. Often you don't want to merge the content of one ticket to another because it may simply be a duplicate ticket. You may just want to close the duplicate ticket after linking it to the other ticket and enter an appropriate comment such as: "Duplicate ticket - refer to linked ticket: ticket#." Each of the linked tickets should display a hyperlink to the other ticket(s) when viewing them, e.g. "This ticket is linked to: ticket#, ticket#, .....
2. You may have different customers requesting the same (or similar) features, or reporting the same (or similar) issues. By "link" the tickets together staff can see all other supporting tickets. Hidden advantages are that staff get a good idea of how big the issue is (how many customers it is affecting), they may also get different user perspectives on the same issue that help to resolve it, and once an issue is resolved you can notify all customers who reported it by replying to each linked ticket.
Hope this makes sense ;)