Feathering Notes:

If you have multiple objects selected, the feather appears around each object. If you group the objects, the feather appears around the outside of the group.

Objects with bevels or contours:

Selecting only the object adds the feather to the outside of the object, not to the bevel/contour.

Selecting only the bevel/contour adds the feather to both the inside and outside of the bevel/contour.

Selecting the object and bevel/contour adds the feather to the outside of the object and the inside and outside of the bevel/contour.

If you want to feather only the outside of the bevel/contour, group the object and bevel/contour before adding the feather.