Based on:
This should be one email or username per line and looking at the code, you don’t need comma.
What you initially did should work. 
Did you see “Your CSV was received and x users will receive their badge shortly.”?
Also, note shortly; this is not immediate. I believe there is a job queue and you might have to wait one day. You can trigger manually the BadgeGrant job on the /sidekiq/scheduler page. It should empty the queue.