[gioele]

I would not call this _more semantic_.

It is definitely a very cool and clean hack (more of these on HN, please), but not semantic at all: in the source there is not indication that the box is pointing at something or where it is pointing.

Looking at the domain name I thought it was a public request for a new CSS property like

  p {
      border-bottom-right-cap: solid-arrow-outward;
  }

[rralian]

I think it's more semantic than a non-content div or image that has no real semantic content, which is what my solution (and most I've seen) amounted to. I suppose ideally some property on the dialog container like 'data-refersto="#indicatedContent"' would be a little more semantic. And eventually that could be implemented directly in HTML and stylable in CSS. That'd be neat.