Not being a sport judo historian per se, I found this quote intriguing:
"Attacks against all joints were permitted in early judo contests...(but) have gradually been restricted in tournaments to elbows only. In 1899, locks of the fingers, toes, wrists, and ankles were banned (knee entanglement or twisting knee locks were banned in 1916). Joint lock attacks were limited in contests to the elbow in 1925..."
-- Judo Unleashed, Neil Ohlenkamp
Elbow locks, the book's author says, allows more opportunity to "tap before injury can occur." It also says that further locks are explored in judo kata. I can't verify this, as I am not a full-fledged judoka, but I am sure some of my readers can definitely speak to this.
I just like the notion of how people today debate the merits of point sparring, grappling, MMA etc., when judo seems to have been analyzing safety vs. realism for so long now. Although I understand certain other techniques have been banned in judo over the years, I'd be very interested in discovering what more recent adjustments have been made in sport judo, and the pros and cons of such decisions.