I worked at a Dodge Chrysler dealer for a short time. Shop foreman came by and saw me putting dielectric grease in the plug boots to help removal in the future. He gave me **** and said it would cause the spark to track to ground. Shop foremen over the years have proven to me to not be the brightest around.
I always like to make life easier for next time. It is like turbo mount nuts that seize on if an antiseize is not used. I always put a dab on the studs. Other guys would ask why and when I explained they would say, "screw the next guy, it won't be me". With that attitude working in shops got too much for me. If every mechanic looked at it like they would be the guy to work on it next time, all our jobs and lives would go easier and less stressful.