No, commenting out that code should cause errors because later code is looking for those variables. In addition, directly editing the code of a plugin is the wrong way to do things, since it means you either:
1) recreate your changes each time you update the plugin, or
2) backport changes to the plugin each time an update is released, or
3) you leave your modified plugin alone, potentially exposing it to security holes, and ignore all future bug fixes, security patches, and new features.
None of those 3 options are ideal, so you should cross off directly editing plugins from your list of potential WordPress practices.
I’ll whip up a new option setting in the next day or so which will allow you to hide the email. In the meantime, the code you want to change is to remove the $wpscst_email variable from $wpscst_username in the code above. Again, I don’t recommend ever directly editing any WordPress plugin or theme. Instead, use action hooks, filters, and your own plugins and child themes so that you can continuously update your site. I can and will add custom action hooks and filters on request, and I am also months into a revamped version 5 of wpsc Support Tickets, so stay tuned.
