Except that images have been linkable since forever, and they are not really "terms in hypertext". Once you start allowing other items than text inside your anchored reference, you have to accept that the relations may become more complicated than a simple, single graph edge. The reference content may in fact be a block quote with a deeper nested reference within itself... and so on.
Images are text, at the academic level that hypertext was originally conceived. That's why it makes sense to click and drag an image into Google search, and why it doesn't make sense to do the same to a random div.
Going back to the img example: What if I want a navbar? The semantically linked thing is not a random div, it is the whole button area, not just it's text. What if it contains a "help with this option" icon with in the area, that is semantically different from it's surrounding button?
The argument is that if an image is "text", then other elements that aren't just words, can in fact be "text", because they have semantic value.
Bold is a style. Hence it being phased out in favor of emphasis (em).
Seriously, your entire argument right now looks like: "there are only three semantic things - anchors, images and text". It ignores the notion of headings, lists, partial references, nested references, sections, etc. These all have textually semantic meanings apart from styling.
Are you just trolling, or are you honestly refusing to acknowledge that there are semantic meanings for things other than the three I mentioned?
Terretta covered it as well as I could have, so I'll just elaborate on a couple things.
Using the word "content" is a lot clearer here: the point is that it's non-structural, rather than that it is non-semantic. It doesn't make sense to hypertext structural elements, but it does make sense to hypertext pieces of content.
Let's say I have a massive corpus. That corpus is composed of text, images, perhaps some audio and video files, whatever. That corpus is structured using markup, by saying "this block is a quote of something else; this block is the header; this block is a list and these blocks are its items" and so on.
That all assumes it's text, of course. If it's a 2d image, that might actually be an image map, in which certain portions are sliced off, defined as subsections (much like an UL tag with LI children), and sensibly linkable. Differently, an audio file might have specific time intervals linked elsewhere; we don't have a UI for dealing with that purely yet (and maybe will never find a reason to have one). And YouTube & co have demonstrated ways of doing video linking. If you link to a specific second of a YouTube video, that's no different from a table of contents in a hardcover book: it's the automatic movement that makes it hypertext.
That's what hypertext is. It links two pieces of content together. An anchor tag is just how we've done it so far.
And I need to emphasize that this is an academic perspective and mostly useful for thinking about how to design a browser's API. And I'm overwhelmingly not qualified to do that. As a web developer, it's mostly impractical to think about this at all: it has nothing to do with developing web apps.
That's not what he said. Also, those are not similar things. A, with or without HREF, can wrap the other two. Images and text are symbols of meaning where the text defines itself as to what that meaning is, and the image defines itself as to what that meaning is.
A blockquote indeed means something, but it doesn't define itself. It just sets off text from other text. It needs text (one of those two things above) inside it to convey the quoted meaning.
Put another way, a blockquote is not content. Text is content, as is an image.
While I agree block-linking seems like an odd way to implement the desired functionality, the idea that javascript (did you mean javascript?) is a more suitable alternative is dubious.
The concept of requiring an entire engine to enable linking from HTML elements just seems dirty, when it could be achieved so much more simply with a universal href tag. For starters, how would one define link targets?
If your concept is that blocks of design should do things when clicked, that idea is valid. Thankfully, we have methods for easily capturing click events on arbitrary and nested blocks--in fact a whole language for handling events across the representation of layout.
Meanwhile, hyperlinks were for terms in hypertext, and A are the anchors around terms, helping you make a TOC and Index within a single document. The semantic meaning of A is, "this is a term" and A HREF is "this term conceptually relates to this other hypertext reference".
Nobody's forcing you to overload that very simple concept, and certainly nobody's forcing you to wrap headers and footers and main divs inside an anchor. I feel that your application of the anchor is broken.