Re: "... anti-stall – sorry, plane pedants hate it when we call it that..."
Its more complicated than that. MCAS was put in because without it the planes had some extremely nasty handling characteristics that are absolutely prohibited, and rightly so, as Electronics R us says above. That wasn't unreasonable, I very much doubt that its the only plane that has similar fixes in software, and as far as anyone can tell that part of it was OK. It wasn't anti stall, it was to prohibit getting in a situation where it would be difficult to avoid stalling. If my understanding is correct it was perfectly reasonable.
But, and this seems to be where it has gone wrong, once they had that system in place they then extended it into another part of the flight envelope to deal with another more minor handling issue, and the scope in which it would come into play was greatly extended, and that's where everything went wrong.