Its much easier to forget about fancy formatting and use only the simplest HTML constructs.
I think for the most part people are after reviewing the recent submissions. It seems like there a only a few commonly repeated mistakes PPs do that confound ePub and MOBI generation: What do to about illustrations in the ePub and MOBI files distributed without illustration. Illuminated Initial Caps Drop Caps Text represented as Illustration for some reason (PP thought the original text looked so cool that some of it was introduced as an Illustration) Equations "typeset" in Unicode/HTML I wonder if instead of enumerating the HTML constructs people are allowed to use if it wouldn't be better simply to enumerate the HTML practices that will lead to trouble? Again, I don't think people are trying to cause trouble, they just get seduced by some visual aspect of HTML without realizing the problems that will cause later.