Managed to score a lot of points once by having a columnar display collapse itself with smooth scroll to make space for additional info beneath it (define a scroll region over the centre part of the display, cursor position to the bottom and print more stuff - with line drawing chars forming a grid the effect was very effective).

Smooth scroll is actually quite easy in hardware, as it's just a case of changing the scan line offset by 1 each frame. A small handful of TTL chips will do it, later a small tweak to the CRT controller, and nowadays about a bazillion CPU cycles to do it in software.

Most quirky, IMO: double-high/double-wide characters.

Most obnoxious, from the standpoint of a terminal emulator developer: origin mode.

Sadly I never convinced the VTE maintainers that it'd be a nice-to-have.

To be frank, it'd require some departures from the original - speeding up to consume large off-screen buffers and slowing down to a human pace when the buffers clear - and, like any extra feature, it'd be a burden to be carried for the foreseeable future, so I completely understand them saying a polite, but emphatic, no.