I played a few matches last night (TDM) and I'm still only at 6. Is the Digger event the only one giving them out?
Alpha playlist was giving credit for each match and local match with guest login as well.
I was playing ranked TDM and saw a few people with the "I made this!" tag (He also had a ghostly retro lancer) and Epic logos as their icon/avatar. I even saw someone with the "Extremely Serious" tag (Extremely Serious 3.0 achievement), I'm guessing he either boosted or hacked it.