In thinking about it, I think you're right - I'm up against the limitations of the nozzle size. With a .4 nozzle, every right angle is going to have a radius of .2 That's not objectionable with details that protrude, but with small vertical grooves it becomes noticeable.
I did a second building with that same double door, and made the grooves slightly bigger and deeper, and the boards an even increment of .4, to see if it would help - it was worse. I suspect that the smaller and shallower the grooves the better, unless I reach a point where Simplify ignores them altogether.
At some point I may get a smaller nozzle, but I don't think I'll do that now.
The obvious answer is to avoid vertical grooves as much as possible, both in design and by printing parts flat.
But I will ask one more thing - I've been using "inside out" for the outer walls to help with overhangs. Do you think "outside in" might give better surface detail?
Thanks for your feedback. CA.
Oh, as far as sanding - too many small details piled on top of each other. For instance - to sand the boards on that double door, I'd have to sand off the door frame and hinges.