Grammatical (or
grammar) pedantry syndrome is an illness or a form of obsessive-compulsive disorder where someone has a compulsive desire to correct any grammatical errors one has made and is
obsessed with taking this peculiar, constant, and vexatious (from the
target's perspective) action.
"Me and mark
ate cookies!"
"You
mean, 'Mark and I ate cookies!'"
"Stop it!"
"
Sorry, I have Grammatical Pedantry Syndrome."