We have two different quotes available: a quote and a pullquote. Technically, the idea is that a quote is something someone else said, and a pullquote is a piece of text from the text of your article, pulled out to give it emphasis as a graphic element.

Our descriptions do indicate this difference—the pullquote is described as "Give special visual emphasis to a quote from your text."—but then we undercut that a bit by offering a citation for the quote, which isn't generally used with a pullquote. From a user perspective, this makes it seem as though both blocks are used for the same purpose, but offer slightly different styling. But then each block also has style variations—so there's lots of potential here for user confusion.

There's also a semantic difference between the two, where a quote is a <blockquote> element and a pullquote is an <figure> element, but that is largely invisible to the majority of users.

It's also been identified as a point of confusion in usability testing: https://make.wordpress.org/test/2017/12/06/wcus-gutenberg-testing-volunteer-feedback/ and it threw me off as well when I first tested these blocks myself.

This has come up in earlier issues (#5947), but it might be worth revisiting for 5.0 in order to reduce unnecessary user confusion.

Pullquotes work really nicely in print, where layouts are fixed, but they make less sense on the web, where people are increasingly reading on mobile devices and duplicating content is a bit weird. There are also accessibility concerns if people are using pullquote for its intended purpose, and duplicating their content. (I think we'd want to add an role="presentation" aria-hidden="true" to the containing <figure>, but @tofumatt may know better there.)

My recommendation would be to remove or hide the pullquote block for now, since its functionality can eventually be replicated by a container block and a nested quote, and it introduces needless confusion for the majority of users.

Failing that, we should at least remove the citation from the pullquote block. Since the intention of a pullquote is to quote from the article itself, a citation doesn't make sense in this context. We may also want to consider the accessibility implications of pullquotes being used for their intended purpose.