The on screen confirmation email is hardcoded to show system generated text or the text from the simple confirmation email.  Any merge fields (like username, name, or address) are system generated.

If you'd care to make a suggestion regarding this issue, Blackbaud has an idea bank our clients can go to and list any suggestions they have for our programs. You can go to http://sphere.ideascale.com/ to enter suggestions and vote for your favorite suggestions as well. This is a direct line to our programming team and they look at this for enhancements to the software.