I don't know anything about grammar honestly. My friend tried to proofread an essay I sent him and I wasn't even sure what he was talking about in a lot of his suggestions. I don't know the rules or the proper terms for anything.
Everything is instinct for me, which means I do bend the rules...a lot. Sometimes I have wholly ungrammatical sections of text that are just denoting my character's state of mind. I really don't care whether my use of commas is correct or not; I use them as I see fit to make my sentences sound the way I want.
I think that's fine, if done well. You see this in published work, including some of the most well-regarded works out there. When it comes to beginners, I suppose the tension is between the point of view that says "Hey, you aren't James Joyce yet, do it the way I tell you" and the approach that says "I don't know if you're James Joyce yet, give it a shot and let's see." Usually, for beginners, the answer is no, you're not Joyce yet, but I lean more heavily toward letting people try to be.