@dunstan@beep So, depending on the complexity and setup (every page is different), you're going to see several potential performance impacts:
1. More nodes == slower performance for the browser (depending on the browser) and DOM traversal & manipulation via JS.
@dunstan@beep 2. The memory footprint will be larger and could stain (or crash) some devices.
3. You could run into a 413 error (Payload too large) on certain lower end devices.
@dunstan@beep There's also potential impacts in the UX space concerning the complexity for users to restyle pages to improve legibility for them and/or hampering “reader view” services.
In terms of studies, I don't know anything offhand. Perhaps @ericlaw might know.