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So my 1988 Paso appears to be consuming insane amounts of oil, on the order of a quart every 250 miles or so. It has less than 8,000 miles on it. I put it back on the road last year, and when I got it, it hadn't turned a wheel since 2003, so almost 20 years. It had a hair over 7,000 miles on it when I got it. It runs beautifully, has good compression (last I checked I think around 160? - I'll check again), and doesn't smoke. No plumes of blue, maybe a bit of black from the exhaust when you jump on it. Years back I had a 1983 Kawasaki GPz750 with the same issue. Good compression, no smoke, went through oil like crazy. From what I could find, Suzuki had that year switched to using very thin piston rings, presumably to help reduced friction. The info I found said that if the engine was run very hot it could result in the rings losing their spring tension. You'd still get good static compression, but after ignition the rings would relax to the point oil could and would meter past them into the combustion chamber and get pumped out with the exhaust, with no real sign of oil burning. That engine ran very well. Eventually I replaced the piston rings, and that cured the issue.

Is this a thing with the Paso engine? And assuming I'm heading down the path of ring replacement, how scared do I need to be that I'll find bad nikasil platting in the cylinders? Beyond plating flaking off, what should I be looking for in terms of assessing cylinder condition? If the plating is bad, does anyone have any experience with getting cylinders redone? Sources?

I don’t know if the Paso came with plated cylinders or not, but I know the company Millennium Technologies does cylinder replating.
A statement copied from their site: “Our core business at Millennium Technologies is our proprietary Nickel Silicon Carbide (NSC) cylinder plating process and cylinder services.”

A quart every 250 miles works out to be about 20:1 fuel to oil ratio........and it doesnt smoke ?
Dont spose there is a #ucking great pool of oil under the bike ?
Paso cylinders are plated and as far as I know they dont give trouble .......and if that was the problem it would smoke , foul plugs and there would probly be oil dripping out of the exhaust joints.
A quick look at the plugs will tell you if its burning that much oil ,and since you didnt mention oily plugs when you tested the compression Im assuming they were ok ?
Make sure the oil filter is tight , and the gearbox output shaft seal is oil tight.
Im thinkin you are loosing oil whilst on the move ,oil dripping off the filter at speed will most likley clear the bike ,and oil leaking from behind front sprocket can be mistaken for residual chain lube as being engine oil most of it gets flung off.
Give your engine and oil coolers a real good clean ........like whole can of degreaser, compressed air and many rags . This will make any leaks easier to spot

Nope, no oil leaks. Well, some minor weeps here and there, but that's it. I'll pull plugs again this weekend and run another compression test, but last look showed the plugs a bit sooty, but nothing more. This is exactly the scenario I experience with the GPz - it's definately odd. It runs absolutely great, with strong acceleration and, yes, no smoke. Normally, I'd expect plumes of blue with an engine that's using this much oil. I expect I'll be pulling the top end apart when the riding season ends, which is only a few months away.

A quick look suggests piston rings are getting hard to find; any suggestions for best sources/whom to contact?

I had the same with my 94 900ss, 1 liter oil every 1000km . no smoking or bad odors. Turned out to be the valve seals which became hard . Previous owner had switched the seal colors, should be black for inlet, green for outlet valves.

Wouldn't surprise me if the seals were rock hard, given the age of the machine and its long period of inactivity. Didn't get time over the weekend to peel off the body work to pull plugs and conduct a compression test, maybe this weekend. Regardless, I expect to find myself taking a deep dive and pulling the heads/cylinders this winter. My only real concern is condition of the nikasil coating. Guess I'll find out!