Heey guys,
I was doing firemaking at falador east bank.
I had npc and player debugging on and after approx 3hours i saw a red dot with a name and combat lvl.
I turned player debugging off and red dot was gone and name was gone.
It was an invisible mod!!!
Proof:
You do know there is an invisibility glitch floating around. He could possibly be abusing that. You never know, and unless you get him to talk, you never will.