The user name should be enough. Not sure you need to include the unique id.
As described, the current portal emails include the the format of Aha! - user name <email ID> to allow us to associate the response with the correct idea. Emails across Aha! use this same framework. Perhaps the suggestion around this is to help with filtering/spotting Idea portal emails as they come through. One potential solution is to set up email filters around the Idea portal name.
Based on the current framework in place, community feedback and current priorities, we are unlikely to make changes in this area.