Not sure if this is gonna hurt me.
I've been self-boosting off of a second console and I believe I have numerous kills for the Not So Seriously achievement but I haven't tracked them. I had been utilizing the Team Skull Shot leader board and figuring that if I got to 31 skill rank that I should have the achievement considering many on that board have that achievement right around 30 or 31. I was as high as 28 tru skill and #30 on TSS leader board and played another match, this time I had a brain fart and didn't kill my other tag, I just took the skulls out.
When I checked the leader board again I was 26 tru skill and #96 on the leaderboard. I'm hoping that some of my kills haven't glitched, let me know if this happened to anyone else, especially if you got the achievement after.