In reply to Chris Aldrich.

This is a good start, but I haven't been able to make it work for me, because something odd seems to happen when I annotate pages in Brave for Android using the via proxy. When I press to start a highlight, then start to drag, suddenly the lower selection handle jumps to the bottom of the page. There's also the annoying thing about the annotation menu and the browser long-press menu overlapping reach other, but that's relatively minor compared to the selection issue.