One way is to have no character ability improvements, only player skill and player experience matters. Like say...tetris, q-bert, pacman or tekken. In this scenario, you skill and experience is always fully portable. I hope Subotai's CLANG is like this.

Another is to limit the communication to human terms. Maybe you occlude all knowledge like jcromartie says, or maybe you realize that nobody ever feels like they have 18.6 strength. They feel weak, strong, or very strong. They feel nimble, graceful, clumsy, dumb, quick, lethargic, injured, smart, etc. Color gradients might be a non numerical way to give fuzzy information about ability. Your character is not a precision machine (unless maybe you're playing mechwarrior)