Ooo, turns out <dialog> can be triggered without JavaScript, the only problem is even if I set it to border: none; (or zero) it still seems to render with a 1px black top border, at least in Firefox. It's not an outline or a box-shadow, either. I can make it disappear by setting the borders to be 1px and white, but it'd be nice if it just did what I asked. I also noticed close buttons don't work unless set to type="button" when inside of a form in the dialog. Not a really a bug, though.