I'm not sure where "ankle protection" factors in, I'm curious how people are perceiving "ankle protection", meaning - what risk scenarios are you picturing protecting from?
Coming off off-road is definitely a factor; you can find yourself putting a foot down on uneven rocks with the weight of the bike on it, and having an ankle that's stiffer than a hiking boot can do nothing but help.
Another factor offroad is if you take a rock, branch, or stump, or footpeg to the shin.
But if you come off on the road, the forces your ankle is likely to endure can be fairly extreme, arguing for extreme stiffness of the ankle, not to mention the amount of asphalt the ankle might grind across.
Not to keep returning to this, but I've spent a long time in action sports, where a fall can easily twist or break an ankle (or leg) - that's from a sort of hyperextension - and that type of injury seems unlikely on a motorcycle...
Likely, unlikely... the only reason we wear gear is because we might crash, and we hope the gear will save us. I was at an on-road accident scene a couple weeks ago where a biker had his leg ripped off. (He did not survive.) Likely or not, twisting and grinding ankle injuries are completely possible.
If you come off the bike and land on your feet, an ankle twist is likely from all the videos I've seen. If you don't land on your feet but stop yourself with your feet, there's a chance of damage there.
That said, many (most?) riders might go their entire lives without suffering a substantial ankle injury, regardless of the level of protection. Most riders don't end up in an at-fault accident, either, but they still carry liability insurance.
It's really a matter of how much you want to protect. Plenty of riders ride in blue jeans, motorcycle boots, and a motorcycle jacket. I want to protect my legs and butt, so I wear riding pants. They don't. It's really up to you and your level of comfort, and what you're willing to risk in a fall.
The other sort of "ankle protection", as Tom's picture shows, the thought of "dropping your bike" on your leg is not a hyperextension.
True. But I'll take my bike dropped on my Alpinestars Scouts over my bike dropped on my hiking boots any day of the week.
To extrapolate that to motorcycling - I was reading reviews on some of the footwear recommended, and hearing complaints about it being difficult to shift and brake with some of these boots that seem to aim to immobilize the ankle
Absolutely true. Well, I've never had trouble braking, but shifting with size 13 boots can be more effort. But it's never stopped me from taking a ride, and I don't think about it. It's more difficult, but it's not hard.
Search youtube for "motorcycle break ankle". There are plenty of examples at low speed and at speed. Most of them are people goofing off, but here's one that's far more like my riding style:
"6 permanent screws and a plate holding my ankle together". I daresay if that guy had my boots on, that would not have been required, and his ankle might have been undamaged.
Again, it's really up to you. Everyone here is projecting their own level of desired safety on you, but it might be more than you want. Some of my best friends foolishly ride in jeans. ;-)