1 回答
The quotation marks can safely be included in the CSS without violating any HTML5 best practices.
First, browsers normally don't display quotation marks when rendering the <blockquote> element. Chrome, Firefox and IE10 apply indentation to blockquotes by default. So it's not like you're removing quote marks that are normally there by putting them in the CSS.
Second, you mentioned the word "style" in your question a couple of times. That's a good hint at where the quotation marks should go.
Third, the ::before and ::after pseudo-elements are specifically designed for adding cosmetic content, like quotation marks. In fact, if you read the MDN page for ::before you'll find that their primary use-case example is precisely about adding quotation marks.