Lemmy admin should add option in the account settings for hiding your username from your posts/comments, and hiding your profile from the public, so noone would be able to see all of your posts in your profile page, and even if someone is using a tool for scrapping posts, they wouldn’t be able to link the posts to 1 user, because the username would be greyed out “anonymous” (and would not link to anywhere). Only lemmy staff would know the real username.

Edit

This feature would be useful for whistleblowers, or users who want to be anonymous (those who often delete their posts/comments and accounts, or have to use multiple accounts to reduce fingerprinting), while others who want to use lemmy as social media and create friendships would keep their username visible publicly.