TIL about the <mark> element (HTML Mark Text element) – an inline tag used for highlighting a passage of text. Most browsers apply a fitting bright yellow background and black text by default. For example (via MDN):

When used in a quotation (<q>) or block quote (<blockquote>), it generally indicates text which is of special interest but is not marked in the original source material, or material which needs special scrutiny even though the original author didn’t think it was of particular importance. Think of this like using a highlighter pen in a book to mark passages that you find of interest.

Quoting a passage from another source and adding commentary is such a common post type on many popular blogs, that I’m kind of surprised this tag isn’t more commonly used. For designers I think it provides an interesting typographic opportunity, and for content authors a helpful alternative to bold and italic styling.