One of the quirks of the #reddit API is that it only ever retrieves 1,000 results from each of the category combinations you can query — which also limits the total history you can see in your profile on the web. For me, with 15 years of history, the few thousand comments I was able to delete were a drop in the water.
So I did a GDPR request, got a bunch of CSVs referencing every post and comment I've ever made there by ID, and tonight's fun project will be to script deleting them all 🥳