> On (2), I do find myself consuming agents' gigantic text responses, writing 8-bullet-point responses to guide them, then iterating that way. It's pretty exhausting. I could see inline comments providing much better ergonomics.

For your 2 plannotator [1] has a nice way to annotate agent messages or documents and its integrated into the agent chat (codex app also adopted the pattern)

[1] https://github.com/backnotprop/plannotator