Um. In Firefox, right-click on the image, select Copy Image.
And how do you insert it into a comment?
I think you're missing the point of images. Their advantage is precisely that they are holistic, a gestalt -- you're supposed to take them in whole and not decompose them into elements.
That may be true of some images but not all.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.