I don’t know about this person’s experience, but there are an overwhelming number of drivers here that don’t notice signals. I can be in the right lane (two lanes in both directions), signal a right turn, slow to turn and they’ll still ride right up on me and look pissed rather than go around.

It gets worse, some drivers seem to adopt an adversarial attitude towards the usage of turn signals and will deliberately accelerate or do something else to make things more difficult to you.

If they’re behind me, they’re risking their own liability.

Otherwise (changing lanes, left turn across traffic), I think it’s more “not ahead of ME!” than about the signal itself.

If two cars travelling the same direction contact each other such that the front axle of one car bumps the rear axle of the other (the car in front), it's usually the car in front that has the safety problem. This is the same principle behind the PIT maneuver.

If there's a rear end collision severe enough that the axles are contacting each other, both parties have a safety problem.

I wasn't talking about that. I meant lateral motion

I didn’t mention safety issues

Irrelevant. They're going 45+ in a 20mph zone.

No, they're going 20-something mph in perhaps a 20mph zone: the author stated kilometers per hour.