What were the signs during extrusion that the filament was being ground up by repeated retractions? I'm guessing this is also work-piece specific issue. I would like to find a way in the Cura visualizer to flag / highlight the retractions in the toolpath view.

Your idea about the skirt line is great. I'm using a brim because I've been having terrible problems with the ABS pulling up and the brim + ABS slurry directly on the plate seems to be working. I would definitely turn this off for PLA.

My understanding is the fix horrible type A is enabled by default and I didn't mess with those settings. From what I read they involve interpreting geometries from the STL and the type A is generally a good thing but can close some holes that were intended to be left open.

As for Repetier-Host... I'm intrigued, but the Mac version wasn't stable when I gave it a brief go and I didn't see Cura support (the Mac version is way behind IIRC). Sadly, the linux version requires a version of mono that conflicts with what I need to run my CAM tools.

Separate from the slicing, I had been using Octoprint on a Raspberry Pi for control, mostly for the web cam (which is really just a wrapper for MJPG streamer). It works for simple manipulations (move Z up, etc.) and for monitoring / setting temperatures, but all of the other features, e.g. starting a print, uploading to SD card, visualizing GCode don't seem to work out of the box. Anyway, since it isn't completely functional, I moved over the Repetier-Server. I'm not in love with the web interface, e.g. it doesn't have a temperature graph, but I've only had it up and running for less than a day so I'll reserve judgement. All I really want is to be able to send files to the printer without sneaker-netting the SD card around the house.