Any mechanic you'd like to add ???

[Dakota]

ASA allows the overhand out to be signalled with the left hand for left-handed umpires because the overhand out is a throwing motion. IOW, they recognize that a left-handed umpire "throws like a girl" with his/her right hand. (Apologies to our female colleagues and athletes - but you know what I mean.)

Perhaps the reason the "non-sell" out and strike "hammer" are not to be given with the left hand is to avoid confusion as to what the signal actually is. I agree that most of the time context should mean the possibility for confusion would be small...

[SRW]

ASA Umpire Manual, Pg. 206 "Communication and Signals"
"Signaling is a very important aspect of umpiring. Decisions are relayed to the players, coaches and spectators using approved signals. The adopted signals are dignified, informative, meaningfull, and therefore, shall be used by all umpires. Poorly executed and unauthorized signals serve only to confuse. The manner in which a signal is given determines, at least to a degree, its ascceptance by the players, coaches and spectators."

ASA Umpire Manual, Pg. 225 Slow Pitch Plate Mechanics "Calling Balls and Strikes", 2nd paragraph:
"A pitched ball that hits the ground in front of home plate, hits home plate, or hits the batter, becomes dead and a non-verbal dead ball signal followed by a verbal ball or a strike signal shall be given.

ASA Umpire Manual, Pg. 239 "Selling the Call...Sell OUT/Sell SAFE", 3rd paragraph from the end:
"A left handed umpire is permitted to utilize their left hand and arm to make the overhand out signal as this is a natural movememnt of the umpire."

(Bold and underlined emphasis added by me.)