The reason we don't give letter grades is that, frankly, what a particular instructor thinks of your writing is irrelevant. We're not buying editors or bosses or anyone else who matters. We are people trying to help you learn a broader skill set. When we think you have mastered that skill set at a basic level, you're ready to move on. As you apply that skill set in your real world, you'll augment and expand it.
Interaction varies greatly depending on the student.
Some students just send in their assignments and we never hear anything else from them. Others ask all kinds of questions and we do our best to answer them. Sometimes, when we travel, we get together with our students in person. Interaction also depends on the number in a class. Our faculty is as good as the faculty at any land-locked institution.