IPv4, IPv6 and reliability

I didn't expect that this would be common enough to see it myself:

What it means is that IPv4 has become (or is becoming?) less reliable than IPv6 as a transport. The web service (a nice professionally run place) detects that my NAT gateway has tried to do something nasty, and blocks some functions from that IPv4 address (or maybe from an IPv4 /24?). Thousands of people use that NAT gateway, because the ISP has more customers than IPv4 addresses and puts all of us behind one IPv4 NAT gateway.

IPv6 doesn't have this problem — each customer gets a unique IPv6 prefix so only the malevolent customer is blocked, the block won't affect thousands of bystanders.