[whatwg] strong and em difference not clear

[Peter Michaux]

The HTML 5 spec doesn't give clear guidance on the choice between
strong and em tags. The explanations hinge on the difference between
the phrases "stress emphasis" and "strong importance". I'd say these
phrases are synonymous. In English we emphasis something in our speech
because it is important. That blurs those two phrases together
immediately.

I searched around the web and other people are confused by the overlap
of these two tags. For example,

http://stackoverflow.com/questions/525168/why-is-u-evil-while-strong-and-em-is-not/525172

Can a better justification for the existence of these two tags be
given in the spec?

Peter