Ah. I missed that part about licking the fletching. I sometimes wet my finger with a little wate (not spit) before combing the feathers on my arrows, but it's usually just a tiny drop--nowhere near as much as what would get into the flecthing if I actually lick it. Wet vanes tend to curve a bit and act like damaged or off-kilter spinwings, intorducing an unpredictable spin into the arrow. Even synthetic vanes do this sometimes.

The sort of archery practiced by Robin Hood is very different to modern, recreational, longbow archery.

The sort of arrows shot would typically be 28 - 32" long, 1/2" diameter, weighing about 3oz and spined to about 200+lb fletched with a 6 - 8.5" goose, swan or peacock feather. The bow would have been somewhere over 100lb - typically 130lb+

The normal rules of matching spine to bow don't apply. Damping one feather would make almost zero difference to a shaft like that.

As we say in the warbow world: "Stiff enough is good enough"

Well, I only said that wet vanes could impair accuracy--not that the amount of impairment would matter when using a war bow instead of a target bow.

Moreover, the feathers are there not only to mitigate the deflection caused by a poor matching of arrow spine to bow strength. In my experience, their most important role has been in reducing the inaccuracy caused by an arrow shaft that had become bent or somewhat damaged by use. Wet fletching can dramatically improve or impede this correcting power--but the crux of the idea is that the effect of moisture on fletching is so unpredictable that it's better not to wet the fletching if you can avoid it.

And then, in cases where you're right and wetting the fletching makes no difference, then what's the point of wetting the fletching in the first place? It's only a waste of good water or spit and won't be any good in compensating for the inherent inaccuracy and lack of power caused by loosing two arrows at once from the same bow.