Electrons are defined in part by having unit (negative) electric charge. What other conclusion would you make from that experiment?

Why does it mean electrons "exist" in any sense instead of being a model that could explain the data? And if such objects did exist, why could they not follow classical mechanics?

Meh, I could also ask you to provide evidence that you're not a p-zombie... There's an undivisible thing (particle) that has undivisible charge (electron) which exhibits properties and behaviour that could not be explained clasically. How do you explain classically (i.e. Newton's laws and no limits on observables uncertainty) electron diffraction and discretized spin?

> How do you explain classically (i.e. Newton's laws and no limits on observables uncertainty) electron diffraction and discretized spin

Now you're changing the question :)

My original point in this was that hacker news poster "powertower" asked for evidence about an electron's properties outside of QM, and I objected to this question because once you leave QM you're in a different kind of universe.