I’m following up to my post at https://forum.sublimetext.com/t/automatic-backup-plugin/32/1#p65398 about issues with quote auto-matching in ST3 build 3067. I’ve been able to reliably reproduce the glitch in the “Better CoffeeScript” syntax (https://packagecontrol.io/packages/Better%20CoffeeScript), where typing a second single quote only types over the auto-matched character inside parentheses. In any other context, I wind up with three quotation marks. A quick skim of the syntax definition didn’t yield up any reasons why this should happen so consistently in this syntax.
ETA: Reverting to build 3066 fixed the issue, incidentally.