Earlier quoted context omitted.
> NAT is like literally Satan. NAT is merely a tool. Using it to restrict user activity is bad. Using it on your home network to preserve your privacy (ie how many devices you have and what each is doing) is good. There are also other use cases (both good and bad) that I'm omitting here.
I get what you're saying, but I still disagree. NAT doesn't help privacy either. There are a million plus one ways to fingerprint or track a web browser without knowing anything about the end user's IP. A modern browser presents a ton of surface area. It's also quite easy to track by externally visible IP or IP prefix (e.g. /24 or /64 in IPv6) if you make certain nearly-always-valid assumptions about the timing and s…
Well at the ISP level, yes, absolutely!
Regarding privacy, your response seems very focused on web browsing. I agree that NAT plays no role there - it's at a lower level. I was referring only to the potential for masking devices - with NAT, there's no way to tell how many (or how few) devices are producing a given stream of traffic. To the extent possible, I'd rather external observers (particularly my ISP) not be able to tell what's going on inside my network or how it's configured.
In case this isn't making sense, imagine a scenario in which your ISP equates simultaneously active IP addresses to number of active devices and then adopts a fee structure based on this. Or perhaps just tries to profile the types of devices that are active on your network in order to sell that data to third parties. For example, identifying how many Alexas or smart locks or whatevers that you have, correlating that with how many devices are streaming or browsing, correlating this with customer demographics, and so on.
NAT is a useful tool for engaging in namespace shenanigans - consider NAT-based load balancing, for example. It can also be used for ill, and I agree that the current state of affairs is unfortunate.