When were you when the UK was kill?

[grue]

I get that

but my contention is that, let's say the Remain/Leave vote in the UK

if you're saying that Leave should have 55%+ votes to be acceptable, you're also saying that Remain needs only 45%+ votes to be acceptable

and that's favouring conservatism over progressivism

the sort of 2/3 rules that happen in Parliament/Congress whatever usually only apply to structural alterations, such as impeachments or constitution changes, where conservatism is understood to be usually better than progressivism. ie, it's generally understood that you need a Very Good Reason to change the Constitution, otherwise it stays as it is.

does this apply to referendums? I would say that people need a Very Good Reason to leave the EU, but they also need a Very Good Reason to stay. otherwise, you're preferring one over the other. if you think both need equal weight, as I do, you require a 50/50 vote