I was under the impression from previous forum discussions that, much like the current direction official rules are taking (non-refereed fouls unenforceable if shooter objects), the amateur/league requirement for avoiding a double-hit foul is gradually becoming: to merely jack-up 45 degrees, regardless of the CB/OB distance (?). Makes you wonder which venerable playing rule will be next to go away just to avoid conflict.
Interesting post, Dan. No area in the rules leads to more confusion than the double hit.
Another rule that makes me crazy is all ball fouls. I recall Van Boening playing safe with the bridge on a 1-ball at the US Open trailing Deuel, if memory serves, 10-9 in the 2017 US Open 9-ball in a race to eleven. The object ball was several feet away and as he lined up for the safe, he grazed a ball that was way below the cue ball, moving it almost imperceptibly, for a foul. It had absolutely no effect on the position or the difficulty of the shot Shane was about to attempt, but the foul cost Shane any chance to win that match.
This should not be confused with what happened with Wu Jiaqing in the 2019 US Open final against Josh Filler, where, trailing 12-10 in the race to thirteen, he nudged an object ball over which he was bridging, and lost the match about 90 seconds later. This clearly raises major issues and was properly penalized.
I was taught many moons ago, when I first learned the rules, that even when not playing all ball fouls, there are some object ball infractions that must always constitute a foul, and the three most common were a) moving a ball over which one was bridging, b) moving a ball around which one is masseing, and c) moving a ball over which one is jumping. If these are enforced, it covers most of the object ball infractions that I feel ought to be penalized.
As it exists today, I think the all ball foul rules can randomize results in our game in a way that doesn't sit well with me. Many of the purists swear by all ball fouls, but it has never sat well with me.