The two most important parts of the language conventions of responding to literature are the direction and the grammar - the syntax. Responding to literature, in any form, is all about making an articulated argument. This is why teachers make such a point to make sure you know your grammar. Ever wonder why peer review and feedback was so important to making an analytical response paper of a work of literature so important? This was why. You have to know what direction you’re taking in the paper, otherwise it’s a wet noodle. It won’t connect if you don’t know where you’re going.
Proper grammar and syntax makes it appropriate for academia. You wouldn’t say “YOLO” in an academic paper unless it was from a quote in the literature, would you?