Infact it is not a bug but a tip for the command "bend" to be better.
Now the "bend" could only bend an object in the plane from the window. Drag the mouse with left click to change the angle.
So if I want to bend the angle a little, I have to change the view.
But we know when I change the view metaseq doesn't show the angle of number.
So I couldn't bend the object in a accurate angle.
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I suggest to change the "drag mouse with left click" of command "bend" as show a new  "angle point".
So the original first and second points decide the bend area. The new third point decide the bend angle.
So I change the third point to get the accurate angle of bend in 3D.
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now the command "bend" is not easy to use. I think the suggest would help the "bend" to be convenient and accurate.
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Thank you for you reading.