1.

In HTML5,

content “must be quoted from another source”

Heydon rightly makes the distinction between block quotes, which (supposedly) quote another source, and pull-quotes, which highlight excerpts from the article you’re reading.

2. No <cite> in <blockquote>

Heydon suggests using a <figure> and <figcaption> to invoke this grouping, which seems the most sensible option.

The <blockquote> cite attribute is generally useless since it’s invisible and most screen readers also ignore it

3. For inline (or “text-level”) quotations, there is <q> instead.

4. HTML is hard

But the developers have no consequences on that.