Yeah the acoustics of just hitting a key on a good mechanical electrical keyboard is very surprisingly loud and propagates downwards through floors quite well. I used one for years but one still has to be considerate. It's indeed not the worst of compromises, but for me I don't see it as being enough to sustain a (classical) piano playing culture - it's life-support at best without the acoustic element.

Whoa. That building must be paper thin then. I know they produce sound (we had one), but that's still worlds apart from having someone practice a piece way over their heads days on end.

Yeah, that building must be absolutely terrible. I have a shared wall with a neighbor who has a baby grand piano and can only barely hear it from right next to the wall.

No, it's a german building, so brick walls, etc.

The irony is better materials cut out more higher frequencies, so without bass baffling, that's all that comes through. It ends up being more annoying. See also: TVs at reasonable volumes annoying people in the next room because it's all fwoom boom grrrscreeecrshhhhh with no context to piece together what's actually happening, and all down in frequencies that are hard to tune out.