~~Yeah, but it affects ALL charisma rolls, so it's effectively just a permanent CHA boost applied directly to the character. No functional difference from naturally high CHA, IMO.~~

Wait.

It doesn't work if target doesn't have LOS, so loophole found, we just have to invent the internet or telephone in-universe to nullify sokka's advantage.

Edit: or drop a permanent orb of darkness over him so nobody can see what he looks like