My theory is the hanger was letting loose, hence the creaking noise for a few pedal strokes, then Blam-O, into the spokes. It remains a mystery. In any case, I ordered up a new derailleur from Excel Sports and finally got around to installing it today...
Depending on your political take - this derailleur is leaning to the left, pointing to the right, or moderately bent. Pick one. Like the current political picture, none of them appear to be great options.
Dead specimen removed, now a nice paper weight.
Newer style Ultegra bolted up, all angular and racy like. Yup, should knock a few minutes off my commute time and I'll be able to leap tall buildings in a single bound.
After the swap and little tweaking, bike was shifting perfect in the workstand. Test ride however, not quite so. A little more tweaking, still not perfect. No time to finish however, since family Halloween festivities were waiting. Busted derailleur projects can't hold up trick or treat time.
Will need to attempt at a later date. Hopefully, the Halloween curse on the Ibis will be lifted by then...