Finally found a few hours to get back to this project.
Since last time, the saw has idled through a couple tanks of fuel, and then another 1/2 tank bucking firewood at part throttle.
Compression is up

...... to a whopping 136 psi.

The math said the pop-up should produce 145+, so obviously the rings are not seating well.
Tear it apart again -- scratches on the exhaust side of the piston. The photo doesn't do it justice, but take my word for it, most of the scratches clock exactly with the scratches on the OEM piston. In other words, I didn't do a nearly good enough job cleaning up the damage from last year's sawdust poisoning incident, which had left a couple of pits and a deep scratch below the exhaust port.
Note the NWP still has about half of its moly coating on the skirt. I'm surprised the moly has lasted this long.
There was new damage, too. A new pit -- a pinhead sized piece of plating had flaked off -- below the exhaust port, that I don't recall seeing before. It's not a good thing to have pieces of plating flaking off and wandering around in the engine.

If the plating continues to flake, then this jug is a lost cause.
Also a new scratch in the upper part of the jug, near, but not directly above a transfer port. The location of the scratch doesn't correlate to anything on the piston or cylinder, so I'm guessing it was caused by some random piece of contamination -- like the previously mentioned flaking plating.
I honed the jug very aggressively this time, and gave extra honing to the scratches and pits. I could still hook a fingernail on the scratch above the transfer, just barely.
I also lightly sanded the high spots off the piston, and lightly sanded the rings. Pic after sanding.
I'll let it idle through a couple more tanks of fuel and re-check compression. There is no reason to be optimistic, but I might as well give it every chance. There is nothing to lose.