Any progress across the wind is typically made
: at a significant ferry angle, so you end up paddling into the wind.

and partially with a side wind lifting the exposed blade every stroke.

: And paddling up wind in high winds, feathered paddles offer a significant
: advantage.
Yes, that is when they should be used.

: I always use a straight wrist. This is proper feathered paddle technique.
: With practice the amount of wrist motion is small even with a high feather
: angle.
I have never met one person who can demonstrate a feather of 60 degrees or more
and not have the control hand wrist bend somewhat when the opposite blade is in the water (without rotating both hand positions which usually isn't done or done well) including one of the top Necky sponsored racing pros I asked to try it. Even the pictures of the olympic racers show bent wrists. Okay for racing, not the best for multiday touring.

: My 210 cm paddle is longer than two boats rafted together so the blades are
: not an issue, the blades hang out beyond the boats.
We often raft three or more boats for lunching, talk on the water, instruction discussions etc.

: I'm not sure what how blade shape is effected by feathering, but the paddle
: float does not need the blade flat with the water in order to float.
In Alaskan/very cold waters we prefer solid foam floats which do work better flat which puts the other blade perpendicular to the deck.

: Can't say that I have ever noticed the blade getting in the way bracing or
: rolling. I suppose it can happen, but with a little it shouldn't be an
: issue.
: I'm not sure how long it takes people to move their wrist a few degrees, but
: I think most people can do it in the time it takes them to raise one hand
: and lower the other.
If it is still "a little" why do it if you are not in headwinds.

We pay attention to a lot of "little" things to make our kayaks perform better, reduce drag, make our strokes more efficient, save energy, prevent hypothermia, etc. This is just another little thing that has better ways or advantages to use when it makes sense.

Learn both, practice both, use what works best and is most advantageous for the conditions and your physiology.
Randy