Nothing about allowed there. It’s about communication & understanding.

You are free to break whatever convention you like. It will just effect your communication clarity.

Understanding that (and how and why too) will help you be more effective.

It’s no different to saying “you can program it that way if you want but understanding the conventions & methods other people use may help you have more readable and efficient code”.

Really. Whitespace around em dashes hurts my ability to communicate? Please explain.

How are you failing to understand "the reader will expect certain conventions so following those will make it easier to communicate effectively with them"?

This is not a hard concept to grasp.

The downvotes show the grammar nazis abound. I'm with Churchill, who famously said of not ending sentences with prepositions that "that is the sort of thing up with which I shall not put!".