Can still be done on the Bakerloo stock. The speed sensing allows the driver to drop the deadman in rheo 1 and hold and release the doors under 7mph. Drivers would often pop the doors early if they thought they were going to slide through the CSDE loop. Other times it's just pure laziness and repetition. Above 7mph you'll get an emergency Westinghouse application and the front console door buttons won't work.
I think it can be done on the picc too. None of the newer stock let you do it.
The 95 stock used to allow doors to be opened at slow speed, although letting go of the handle at the last minute was never possible. Since the resignalling it’s no longer possible. Still possible on the 09 stock, and indeed happens frequently, and just about possible on the 92 stock too.
Something else not seen so often on LU nowadays is speeding. In times past it was virtually standard practice to get the train “off the clock” at certain locations, for example heading south from High Barnet to Totteridge it was possible to reach over 60 mph, and the Hendon tunnel heading northbound was another good place to get some lively running, although most drivers would take advantage of the tunnel to brake down to a more manageable speed before the open section where there was a signal which tended to remain “on”!
Another thing sadly missed on much of LU is filament lamps in signals. The colours emitted by LEDs are distinctly different, and whilst mostly fit-for-purpose they aren’t as pleasing on the eye IMO.