It looks to me like it is having trouble stripping it because either the image has a php extension or possibly something to do with the query string. Also, when loaded in an img tag, like above, it displays a broken image. Do you know of a solution to strip that image?
I have tried stripping the following image, from the same page, and it works fine:
Notice that image has an actual image extension and no query string.
Also, when these rules don’t work in Full-Text RSS, it’s always a good idea to check the source HTML (right click on the page and click ‘view source’) as this will show you the raw HTML without Javascript being applied - which often adds/removes elements. Full-Text RSS only deals with the raw HTML. If you prefer to use the element inspector in your browser, you can try disabling Javascript, reloading the page and then using the inspector to see if it still shows/selects the same elements.
Our site config builder will also try to load the page without Javascript, so that’s a possibility too: http://siteconfig.fivefilters.org