Those lines are in fact suppose to be there when you enable hitbox visibility (f3+b). Blue indicates where the player/mob is looking and red indicates eye level
I updated to 1.8.1 when it was released, but yes it should be the same thing if you hit f3+b in 1.8.0. A quick google search will tell you the same thing.
I can do that easily... it just causes lag for me. Also, I've killed a hacker before... and it was EASY. On another server, I was playing a game, and there was a speed/fly hacker. It was easy to detect where he was going, like a bird and without hacks, but the speed/fly hacks was all they had. No range, no aimbot, no resistance, nothing else. Just fly and speed, and I killed him.
As much as that makes sense, I don't believe that is right. For a critical hit to occur the player only needs to be falling back down from a jump. The red line was put in so players could use viewpoint of other mobs in gamemode 3 in the aid to help make farms that work by using the mobs sight of something. Example: An endermans ability to see and agro to an endermite.
