[whatwg] Double meaning of the <u> element

[Andrés Sanhueza]

The <u> element was made conforming due to widespread usage and for
some cases were other elements weren't suitable. However, I feel that
the current definition is not very clear, as it gives two somewhat
unrelated used for it: misspelled text and proper names on Chinese. I
believe that is fine if is one or the other, but by the current
definition seems that the purpose of retaining the element is merely
were to underline needs to be used to represent something regardless
what it is, which seems inconsistent with other similar tags that are
better defined to have more finite purposes that aren't based on the
fallback presentational look, even if relevant at the time of defining
those. By the definitions seems that proper names and book names are
suitable to be indicated by <b> and <cite> respectively; or some new
element altogether. I'm aware that the fallback look is an issue, yet
I believe it should be resolved in a more consistent way.