What you don't take into account is that in oficial election the 50%+1 don't take in account the abstain and blank vote.
Anyway I don't think this apply for our system.
72h + 20% have my vote too.
Yes, the 50% vs 10/20% boils down to how the abstain votes are handled...
with a >=50% system:
1750:1250 pass
2000:200 pass
1500:1000 fail
750:0 fail
with a +20% system:
1750:1250 fail
2000:200 pass
1500:1000 fail
750:0 pass
I would personally prefer a low-turnout vote like 750:0 to fail rather than pass... and a high turnout vote like 1750:1250 to pass rather than fail... just my 2 cents