After some investigating, I've discovered that beer stone (calcium oxalate, mostly) doesn't just taste vile, it's highly toxic. Plus it's ugly.
As if that wasn't bad enough, it's also incredibly tough & tenacious. TSP didn't touch it. Easy Off plus pressure washing peeled some of it away, and a good long soak in OxiClean softened it up enough that a scrub brush plus pressure washing got rid of some more. Chemicals plus lots of elbow grease will remove it…where you can reach.
Barring heroic measures, such as blasting the insides of my Sankey kegs with, e.g. crushed walnut shells, can anyone tell me what WILL remove this poisonous dreck where the hand of man cannot go?
[ edit: in my distress & aggravation I forgot to add "Thanks in advance, any input would be much appreciated! ]