Suppose you want to bold something for stylistic reasons. <strong> isn't right, because the boldness isn't really for a strong emphasis, and you don't really want a screen reader to treat it differently.
You could use <span class="bold"> or <span style="font-face: bold;">, but that's just a more verbose version of <b>.
> Suppose you want to bold something for stylistic reasons.
The whole point of the article is that you should use css for style and html for structure and semantics. Don't use markup for style. Have separate css file for that.
If you don't care or understand why that makes sense, just use bold.
But it is unavoidable to have to use markup for style.
You have to use some markup to indicate the span that needs to be bold. Yes, you could use a <span> instead, but that is still using html for style, and conveys less about the purpose of the tag.
You could use <span class="bold"> or <span style="font-face: bold;">, but that's just a more verbose version of <b>.