If you look through tube manuals under Installation and Application the only things stated are the socket pin counts and whether or not the tube can be mounted in any position. Since "touching the glass" is not stated (or "do not touch if they glow") you can assume it's something too obvious to print.
Can you touch the tubes?
I was talking to someone at the tube store about replacing some KT 150 tubes and he said it was perfectly fine to touch the tubes.
I've always thought you're supposed to handle these things very carefully with white gloves or a microfiber cloth.
Handling them with my fingers makes it easier to pull them out , insert them more securely.
Does it really matter if my fingerprints get on the glass or should I clean them off with a microfiber cloth after I touch them?