Counter question, what is the use case here?
I have only ever needed this feature with NSFW content. In Lemmy I have easily and better way resolved it by having another account with nsfw instance. This creates even better outcome than the multi community feature. All clients easily support two accounts, and you can switch between them in few presses.
If archive.org, or any other web scraper is able to pull personal information from a site, it means that the site is already breaking the GDPR.
GDPR protects personal information, not public texts.
Because instance holds identifying information about EU citizens (email, nickname), it means that the instance owner is the registery holder, and they must comply with GDPR.
I believe email address of the user is not shared between the instances, what makes things quite good. Nicknames are bit more problematical, because they can be considered as personal identifier.
Some GDPR experts maybe should write template registery document that instances can use. And the delete of account should be handled between instances. Posts do not need to be deleted, but nick should be changed to [deleted]
GDPR only applies if the data can be linked to individual.
Only thing in Lemmy that identifies you, is your email. Nickname is not personal information, you cannot be identified from it. If the email is not transferred to another instances, there should not be problem with federation. If user requests GDPR erase, instance just deletes the account, and email linked to it. After this the user is not anymore identifiable, and GDPR is happy.
This is just plain stupid.
Forcing browser to block certain sites is like making car manufacturers make the car shutdown if you are trying to smuggle foreign cheese in to France.
Tech illiterates making the decision here.