Assessing a penalty for inquiries regarding exceptions to deadline policy
A colleague had a phrase along the lines of:

"Any email question or request that is already answered in the course documentation will not be replied to".

Seemed to work well for him.

But I would not do any type of downgrading for that.

Students do talk to each other and it soon gets around "well don't send that, as it won't be answered.."

Relevant questions that did warrant a response did get answered to the student and, sometimes, repeated to the class as necessary.