> Protonmail fiasco

Not a fiasco as they're required by law to keep IP logs. You can disable the logging of IP sessions in the PM dashboard, but you can't guarantee that PM will not keep logs, since their servers are all Public Internet Facing. The only way Protonmail is 100% zero knowledge is to be a 100% a dark-net/Tor service, which immediately turns off 99% of their users.

If you misled your users into thinking that this isn't something you would do, but as soon as shit hits the fan and the PR makes it impossible to keep the ruse going. It's a total fiasco to that business' marketing department.

my understanding is they only logged the IP details after receiving the Swiss LI request and did so only for the user in question.

I'm sure that makes the one user feel all warm and fuzzy. Also, what about next. Or the time after, or after or...