The major culprit in ugly image reproduction within feeds is WordPress itself. Even if you’re using the code editor to produce your posts, WordPress will automatically wrap standalone images (centered ones, presumably) inside paragraph tags along with any text that follows. The end result is an inline image that is followed by a semi-broken line of text in just about every feed reader. 😀
Well, here be my caption, matey! 😀
The bottom line is that your feed content can be styled acceptably without introducing evil measures like the hspace and vspace attributes that “force” compliance in just about every feed reader. This day in age, solutions that involve deprecated HTML are no longer acceptable, as we have to find ways to become better publishers, all the while adhering to established standards.