It's as simple as it sounds. Pasting a PNG from Google images into GIMP turns the alpha channel to black.
I've kind of managed to get around this limitation by using Layer>Transparency>Color to Alpha and selecting black. The problem is that black edges also get turned transparent. How can I fix this?
BTW. Try to copy this image from this question with the mouse right click option Copy Image and paste it to GIMP or Photoshop to see does it happen in your web browser.