I remember once signing up for Disqus (I think), or some other “combined” commenter SaaS.

After I had entered my info, but before completing the process, it said “We found all these comments out there. Are any of them yours?”

It displayed a list of ancient stuff; a lot of it posted anonymously (I thought).

I was horrified, and immediately binned the signup.

The Internet can be a downright creepy place.

Hear hear, there are old usernames that I wish I could delete from HN.

Please, no. It makes sense to remove username from a post. Removing content is horrible.

Sure, but it could revert the username to Anonymous Coward, like other sites do. The acid test will be when someone decides to make it a GDPR issue, then HN will need to pull its finger out and implement this simple function users have been asking about for years.