I don't think I've ever tried to post an image other than simply right-clicking on it, wherever it was, doing the "Copy image" and "paste image" thing, and if I couldn't see it in my post I assumed no one else could either and I'd try finding the image in a different place and copying it there. Whenever I've tried posting an image by using the "Insert image" button and pasting in a URL, the image never posted - just the URL.
The only member's images that I can recall not being able to see are those that Peter posts in the Military Themed Pics thread, and I know other members have had trouble seeing those, too.