I'm mostly asking to see how I can adjust my workflow with juniors because I sometimes find myself drowning trying to maintain a decent codebase - not trying to be accusatory.

I generally use MRs as an opportunity to give feedback like how you'd get feedback on a set of math problem statements. I inferred from "rarely do I ever really leave commentary" that you're not using MRs as a training tool. How else do you train junior engineers?

For context, I work in the financial industry where mistakes are costly and users are hostile so the "accept & merge" workflow may not be for me.