scholiast (n.)

• annotator
• carper
• caviler
• censor
• cicerone
• cognoscente
• commentator
• connoisseur
• critic
• cryptanalyst
• cryptographer
• cryptologist
• decoder
• demonstrator
• dragoman
• editor
• editorialist
• exegete
• exponent
• expositor
• expounder
• faultfinder
• glossarist
• go-between
• guide
• interpreter
• lexicographer
• muckraker
• publicist
• reviewer
• translator