This would be a great addition to Moodle.org, one of the largest Moodle sites in the world (but with no way to be removed from the site unless you’re spam or a bad-actor). Bas Brands is the developer/maintainer of the local plugin which allows Moodle users to choose to delete their own accounts.
For any self-registration site, whether offering free or paid services (through courses or membership) this might be a considerate offer to your users in the case that they create a profile and then don’t find continued use for it. Not to mention it’s an easy way to ensure that the users on your site are self-selecting to stay users on your site.
To date the addon only works with Standard Email-Based Self-Registration.
Check it out at https://moodle.org/plugins/view.php?plugin=local_goodbye