XF 1.2 Displaying username on account upgrades description



I have created few account upgrades on my forum that include styling options for their usernames.
In order to demonstrate for the user how they would look like, I would like to be able to display their username in the description with these styles.

For example, I have <span class="premiumGlow">Username</span> in the user upgrade description where the Username should be replaced with their username if they're logged in.

I tried adding {$user.username}, but that didn't work. Instead it just displayed that string.