Hi Mark,
To be honest, I don't really understand why you are getting zero length arcs - are you not using --remove-short-arcs?
If I use remove-short-arcs, the messages will go away. But I am not sure if I am satisfied with that as a solution. Based on the error messages, I did fix some 30 or 40 crossings where the junction node was missing and one of the roads had two nodes very close to each other. It would still be nice to get warnings, but I guess that separate validator tools (such as the JOSM validator plugin and http://keepright.ipax.at/) are a better option. I looked at StyledConverter, and passing additional attributes to the imgfmt domain looks a little complex. A similar conversion would have to be done in the MP format as well. So, perhaps I should forget about this idea after all. Marko