I'd guess it means you've got X amount of tags from that specific player, otherwise once you get high ranked you can never get them.
Yes, as you get more tags from the same player, it goes through bronze, silver and presumably gold. Not sure what the number is for each level.

but its how I got my games added
M4 damage isn't even that high... it's just the accuracy which makes it lethal. I haven't seen too many M4s around either