In Europe GDPR gives you the right to have all your data deleted. All you do is send in a request and SO has to remove everything of yours, not just anonymize it. There are some exceptions for legal reasons, eg where financial transactions are involved, but comments should not be exempt.
It’s not a question if encryption fails, but when. Paper ballots are anonymous by design, unless you mark the ballots they are untraceable. Digital ballots don’t have that feature.