My suggestion is to ask them to fully explain the reasoning behind their comments, rather than just lobbing change requests into your code submissions. You can

My suggestion is to ask them to fully explain the reasoning behind their comments, rather than just lobbing change requests into your code submissions. You can frame it as wanting to learn, grow, and understand the processes necessary to create good code. They have to either shut you down and be unhelpful, or have contradictory explanations that they give forward. Hopefully it actually is a good-faith interaction and just a breakdown in communication. If not, though, putting someone on the spot to explain their actions is a good way to generate documentation that they're acting in bad faith. This works with mean jokes, too, fwiw