It makes sense to make Rank or Progression invisible. Rank did mean more in Halo 3 than progression in Reach, but both had drawbacks from boosting and other problems.
What would be great is if what was displayed to other players was your K/D ratio from your last 10-15 games. This way, people can see how their teammates have been doing recently, and each player can see how they are getting better more immediately.
The ratio would just have to include stats from real competitive lists, and exclude stats from Grifball or Living Dead. Those lists should be separated completely from competitive lists, that way people couldn’t pad their stats with them and would feel more free to just play the game without consequences. I hate how many people just quit or AFK when they start out as the zombie.
Anyways, having your average K/D ratio for the last 10-15 games would be a great incentive for new players to keep on playing more games to improve their ratio and get older players to keep on playing as well. I know I’ve seen players on Reach who are way negative when you look at their stats but wreck in the game because they have been able to improve. The average gives a better view of true skill, while still allowing players to see their improvements.