Thanks everyone. I was able to easily swap out the rear pads in about 15 minutes. Next time, it'll take 10 minutes.
My OE pads had about 12k miles on them and while they weren't worn to the limit, I was stunned at how damaged they were. The trailing edges were beveled and very rough and crumbly -- the material easily broke off in my fingers.
I replaced the pads with another set of OE pads (P/N 43105-MWD-425). I also replaced the rear caliper mounting bolt per Honda's recommendation (P/N 90180-MN8-006). The bolt comes with some thread lock on it. I could have reused the original bolt but didn't mind replacing it. Total cost of parts was $43.00.
Replacement is very straightforward:
1 - Press the piston into the caliper by pushing the caliper inwards, towards the wheel (the caliper only has one piston, on the outboard side).
2 - Loosen but do not remove the pad mounting pin (8mm head).
3 - Remove the rear caliper mounting bolt (12mm head).
4 - Remove the pad mounting pin.
5 - Rotate the caliper upwards, towards the front of the bike. If you've compressed the piston sufficiently, the pads will simply fall out.
6 - Clean up the inside of the caliper.
7 - With the caliper rotated upwards, slide in the new pads. Be sure they engage the spring on the upper surface of the caliper, and be sure the tangs on the pads hang on the front of the caliper. It's easy to see what's happening while the caliper is rotated upwards.
8 - Lower the caliper onto the rotor.
9 - Apply a tiny dab of grease to the tip of the pad mounting pin. Reinstall the pad mounting pin through the holes in the pads and the caliper. You'll need to press the pads up against the spring for the holes to line up. Don't fully tighten the pad mounting pin just yet.
10 - Install the (new) rear caliper mounting bolt. Torque to 16 lb-ft. My 1/2" drive torque wrench wouldn't fit, so I simply used an open-end 12mm wrench and did my best.
11 - Tighten the pad mounting pin. Torque to 13 lb-ft. Again, my torque wrench wouldn't fit, so I used an open-end 8mm wrench.
12- Press down on brake pedal to extend the piston and set the pads against the rotor.