How to remove your Metafilter account
From their FAQ it becomes apparent that you cannot really delete your account. It’s more like account deactivation, and your data is retained.
For more info, check out: https://faq.metafilter.com/#120
Helpful Trick: Removing online data
Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact Metafilter and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).
Helpful Trick: Remove third-party logins
If you signed up for Metafilter using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Metafilter. Click here to find out how.