[estel]

Going back to the semantic movement, strictly speaking em and strong should be used to encapsulate text with stress emphasis (when spoken) [0] and strong importance [1] respectively, and these properties would not necessarily be represented by italic and bold fonts (though, by default, they are).

A better choice for bold text that you don't think qualifies as "strong importance" would probably be the <b> tag, which denotes a "span of text offset from its surrounding content without conveying any extra emphasis or importance".

[0] http://dev.w3.org/html5/markup/em.html [1] http://dev.w3.org/html5/markup/strong.html [2] http://dev.w3.org/html5/markup/b.html