Noble, he means that players can still see your name tag. JANEEMO, I believe it is to prevent trolling, and because of a Minecraft/Bukkit thing.
You can see name tags because of a plugin we use, that is how you have colored names and your rank above your head. Nametags doesn't go away when you do F1 either.
this is because of people like *cough cough OBZ cough cough* who liked to go invis on 1.7 survival all the time... and nuble just had to take all the fun away ;-;
SOLUTION: When using invisibility potions you can become completely invisible (without having your nametag showing) by disguising as any mob. However, you must be a donor and have the /disguise perk to do this.