Feathered selection without creating transparent gaps

[peterolph]

Hi

I'm trying to do some basic photo modification but I'm hitting this problem with the "Feather edges" option for the select tools where it's leaving transparent gaps. What I'm doing is:

1. Use the free select tool with feather edges turned on to select a foreground object from a photo
   
2. Cut and paste the selection to a new layer, leaving a transparent hole in the original
   

In my head, if both layers (foreground and background) are displayed, the result should look exactly like the original, the feathered edge of the selection fading into the feathered edge of the remainder exactly. But what actually happens is a little border of partially transparent pixels appears like this:



The original picture here was just a plain green test square that I selected a rectangle out of.

What am I doing wrong?