I've never seen someone misinterpret a hand pointing in the direction a person wants to go. It's about as basic as you get. Even dogs understand. But my wife and friends started noticing people who have issues with the L-shaped right-turn signal. They know they have to use some kind of kink in their arm and raise it up but just can't seem to get it right. And they use it despite there being a perfectly good alternative.
We can blame this all on our obsession with automobiles. I'll explain.
A right turn signal is supposed to look like Option A, according to many governments:
or Option B, the "alternative" right:
Even the Ontario government recognizes that Option A is ridiculous so they let the sorry folks who can't figure out Option A use Option B. But only to be used in emergencies. Or if you're a child in which case the government tells them to use Option B as the first choice (and Option A if they're missing a right arm?). But when you're an adult you put childish ways behind you and get behind the self-evidently superiour L-shaped signal. For some unrevealed reason.
But we've even seen some really interesting in-the-wild examples where the L-shaped signal has morphed into new forms. (I drew them for you with my expert hand, since we've yet to catch them in the act with a camera):
So why do we tell people to use the left hand for signalling right?
Using the left hand to turn right came about because of cars. Drivers needed hand signals that could be clearly seen from behind, which meant that only the left hand could be used.
Yet when signal lights took over the hand signals were relegated to very rare occasions when the lights were broken. In my years of driving I've yet to see a driver having to resort to these hand signals. Yet ironically, this ill-suited custom, is foisted upon fresh, inexperienced cyclists as the "proper" way. CAN-Bike and other courses even make claims that the L-signal is even more visible in some situations. As a former CAN-Bike instructor, I confess to filling students heads with such baseless claims. I've yet to see any proof or study. Without such, it seems to me to be a justification after the fact. If cars hadn't been invented would we have independently invented the L-shaped left hand right turn signal? Who knows, but I think it's highly unlikely.
The automobile-derived signal is just so counter-intuitive for anyone on a bike, that unless people get specific training and remember it correctly they will invariably get it confused. They want to correct it; it seems wrong. But they just make it worse. Some even know that pointing in the direction they want to go works so they try to adapt a substandard signal into something that works. The funny collision of meaning happens when they attempt to stick to what they learned was "proper".
What is so important about the automotive right signal that we need to force it upon everyone biking despite the confusion? I can't think of one good reason.
Folks: just point in the direction you want to go. We'll all understand you.