There's always a tension between fairness and stability.
In a perfectly fair system you can end up with dozens of small parties, each having small number of people in parliament, struggling to find majority for a government (see last elections in Netherlands).
That's why some voting systems are designed to give a winning party some premium over their vote percentage.
The supposedly stable system has led to 3 nation elections in 7 years (probably another one this year too) and 2 hung parliaments in the same time. Meanwhile Germany and many other countries have very stable politics with proportional representation.
To add to this, having a system which has to learn to work with other parties, negotiate and compromise is a good thing. MMPs supposed downsides are not necessarily so.
But it does mean that fringe extremist parties can get pet policies passed by holding their partners feet to the fire that the majority of the population wouldn't vote for
Its why NI doesn't have abortion or the same rights for Gay people its down to the Ultras in the DUP as Churchill Said "nothing so loyal as an Ulster "policeman"
> But it does mean that fringe extremist parties can get pet policies passed by holding their partners feet to the fire that the majority of the population wouldn't vote for
Evidence for this: CSU in Germany (the quite-a-bit-more-right-wing sister party of Merkel's CDU).
Evidence of it would be present in just about every MMP government ever formed. Here in New Zealand it's present. Sure, the tail wags the dog a little, but if it happens too much the larger party in government loses votes next election.
Unfortunately with increasingly divergent views we have now ended up with three consecutive elections with no solid majority. We've ended up in the same situation, but with less fair representation.
As strange as it seems we may not have had brexit if UKIP had had representation proportional to their support. The reason we ended up going down that road is a large number of Tory MPs feared UKIP. In a proportional system that may not have mattered so much.
That's actually an advantage of British voting system: it makes issues that are important to a large minority of voters impossible to ignore.
Had UKIP had proportional representation in parliament their demands could be ignored forever. And while in this particular case Britain could be better off that way, it is a wrong thing to do in general.
I'm not sure they would have been ignored, perhaps they may have had enough influence to stop it becoming such a big issue.
I was strongly in favour of remain but I can see some people felt they weren't benefiting from the UK being a member of the EU. If they had been given a bit more attention early on we may not have ended up in this mess.
In a perfectly fair system you can end up with dozens of small parties, each having small number of people in parliament, struggling to find majority for a government (see last elections in Netherlands).
That's why some voting systems are designed to give a winning party some premium over their vote percentage.