I don't think it's over-extrusion. The clue, I think, is that other than the 'zits' in specific areas the prints are fine - a calibration cube, for example, looks fine, as do wide areas of other prints, so in general extrusion is properly calibrated (diameter, temperature, etc.) - the issue has to do with something specific that S3D is generating around retracts, different from all the other slicers I've used. Turning up retraction (from the default 1mm to 2mm) seems to help a little, but the prints are still pretty ugly. So any advice there is appreciated. I'm surprised at the quantity of retracts (when I turned on 'show retraction moves' they are the spheres in the path, and they're all over the place.
Here are the relevant settings (which were the same for the earlier photo):
One thing I did notice when inspecting the gcode is that S3D is (at least in this one part) placing some of the infill the outside, which would explain the odd very long "blobs". They're the green lines in this screen shot:
Using version 2.2.2, but consistent with what I saw earlier.