If you delete the “Click Email Link” goal:

Then your EXM click-through events will not be tracked. This came to light when looking in the contact interactions when trying to find out why the click events were not being processed. All the other events such as Email Opened were showing up, but the text “Page event definition Click Email Link not found” was appearing as an event in the Interactions array on the xDB contact.

Historically, as far as I am aware, these goals were just examples, but it appears that EXM has a hardcoded dependency on this goal. It should probably be protected or put into a sub-folder for EXM. For now, though, if you want click tracking on emails to appear in your stats, don’t delete it.