Thank you for this suggestion.
I remember when reddit launched that new design, I just about stopped using reddit at that point because it was so slow on my aging laptop. Of course I was too addicted to actually stop.
As Andrew said it's not really something that fits well with what PieFed is trying to do, at a technical level. It could be done within our existing technology framework but it would be awkward and brittle. Also I fear things wouldn't stop there - soon we'd want the comment form to submit a new comment without reloading the page, or navigate elsewhere too without reloading, etc and at that point we really need what Andrew said with an API and a proper frontend framework. This would mean higher tech requirements to use PieFed as well as more skills needed in the development team and a more complex development environment that new developers would need to set up before they can contribute.
I've got my eye on the possibility (necessity??) of having an API but there's a bunch of underlying code changes that need to happen first. It'll take time.