In working on some code debugging, I noticed that the preferences were not loaded as the program was first using them. Among other immediate issues this had blocked some debug toggle code from ever being invoked.
https://bugs.launchpad.net/inkscape/+bug/367752
As the program starts, preferences are just set to the defaults but not loaded. Then part-way through startup they *do* get loaded. So among other things bits of code might be initialized one way and used another.
It would be very helpful if anyone who is looking into a bug might check to see if this is complicating the issue they are working on. If so, then there might be a few cascaded bugs we can reproduce now and then close as soon as the prefs initialization is fixed.