tl;dr - If you use electrical contact cleaner on your keyboard, verify that it leaves no residue before applying it to expensive microswitches.
Long term update! Guess what happened to the gummy, tacky cherry browns that I shot with WD-40 six months ago? Nothing. They're fine. Nice and smooth. So it worked. It's a nice board again, I use it daily.
This week I notice my other old Kinesis (serial 30034PMD) has started to feel tacky and gummy on a few keys. Stupidly, I decided not to use WD-40 this time, as everyone on here swears it's terrible. So I used an electrical contact cleaner. "Safe on plastics! Quick drying! Leaves no residue!" I figure this is safe, all of it will evaporate. Guess what happened to that board? Sticky city. The contact cleaner did not evaporate. It left a sticky residue, the board is near unusable.
Now that there's nothing to lose, I'm hitting all the switches on 30034PMD with WD-40. It will either remove the contact cleaner residue or it won't. The sad thing is, of these two Clinton-era Kineses, 30034PMD is the one that appears to have had an easy low-mileage life. If it's done, I killed it prematurely. Learn from my mistake.