> Considering that Glimmer goes quite far in optimizing stuff, at which point would it perhaps make more sense to just emulate HTML elements on a pixel-level?
Even if this could be done with reasonable performance (and people have tried this), you shouldn't do this in any browser environment. You can't possibly emulate the behavior of every browser in a satisfactory way; you'll end up behaving gratuitously differently, with subtle breakage of platform conventions, browser conventions, user expectations (including potential extensions), hardware requirements, scaling, rendering, and accessibility.
Even if this could be done with reasonable performance (and people have tried this), you shouldn't do this in any browser environment. You can't possibly emulate the behavior of every browser in a satisfactory way; you'll end up behaving gratuitously differently, with subtle breakage of platform conventions, browser conventions, user expectations (including potential extensions), hardware requirements, scaling, rendering, and accessibility.