It's perfectly fair and it's not weighted. It just means that a Brexit party supporter can vote for them free of worry that he might be splitting the right wing vote and allowing a libdem to win the seat. If brexit wins, great for him, but if they get a low vote share then his vote is switched to the Tories, if he chooses thus.
Ditto for Green Party supporters, a vast number of which Im sure don't vote Green because they don't believe they can win. This way you can vote Green in the knowledge that your vote will still eventually be counted for one of the parties that eventually come first and second.
Or in NI, if you're a unionist you can vote for either the DUP or UUP, putting the other second, relieved that you won't be splitting the unionist vote and allowing Sinn Fein to get a seat with less than 50%.
In the last election I didn't vote for my preferred party because I wanted to give the best chance of beating the Tory. That's not healthy democracy, and has the added problem of not allowing the smaller parties to strengthen for the future.
You get the picture.
Yes, I'm beginning to understand now....that;'s is very nicely explained. Thank you That's called 'preferential voting' is it?