More realistically, commenting it by default would be IHMO a good idea.
A friend of mine who currently learn rails and angular by himself got bitten by it. And angular is definitely not the only JavaScript framework / plugin that don't work well with Turbolinks.
It's a very nice gem for some use cases but a terrible default.
I'd have to agree, having it on by default doesn't seem like such a good idea, omakase or not. There are tons of situations where using turbolinks spells trouble.