re: "...If the timing is affected, though, wouldn't it be pretty obvious when the harmonic balancer fails?..."

I might have miswritten -- sorry about that :-(. It doesn't really affect the ignition timing, but only appears to affect it, if the harmonic balancer fails. I wrote, "...since the ignition timing mark is on the outer ring, the timing mark wanders if there's slippage because it's [meaning the timing mark, not the actual timing] no longer synchronized with the engine's timing belt and other shafts...."

Actually, the ignition timing is still synchronized by the timing belt linking the distributor (driven by the intermediate shaft) to the camshaft and crankshaft*. However, the timing mark (revealed by a strobe light against the timing scale on the timing belt's cover) is on outer ring of the harmonic balancer, and since that becomes loose and slips, it no longer indicates the true ignition timing and just rotates around the circumference.

And that's also why a chalk mark, drawn as a radially drawn line on the balancer, will not remain aligned.

[ * your '88 is applicable to that sentence, but for others reading this who may have a '89 or later, ignition timing is no longer determined by the distributor and intermediate shaft at all, but rather by the control of the car's computer (which also takes care of advance and retard electronically instead of a distributor's weights, springs and vacuum diaphragm) with information from the Crankshaft Position Sensor on the bellhousing, sensing the flywheel's tone ring.]

Hope this helped, and sorry for the misdirection of my prior writing.