The website also states that „properly anonymized data“ is not affected by the GDPR.

The only things from that list, that should be posted on a public internet forum, are race, gender and political views anyways. And it isn‘t really possible to identify a single user based on these data points

By submitting content to Reddit you also granted them an irrevocable license to use it (according to their ToS) and Art.17, 3a of the GDPR protects data that is not identifiable from deletion

But I guess it‘s worth a try. Maybe their DPO is a nice guy