I noticed that when I merge one ticket into another, the non-primary ticket gets a status value of "Closed." In and of itself, this is probably okay, but I would like to suggest that you offer the option of an alternate Status so as not to skew any metrics.
For our needs, I would probably want to use a Status of "Merged" or "Closed - Merged" just so I can keep everything accurate.
This can be a Help Desk setting, such as "Set Status of Merged Tickets as:" and let the admin chose the Status (e.g., "Closed Merged"), or simply allow the agent to select the Status value as a part of the Merge.

