I guess you'll have to do it with browser automation. I assume that's possible?
Rate limits are also quite low so it might take weeks to delete. Many subs will automatically ban you if you edit a comment to say something like 'redacted by' (ex: https://www.reddit.com/r/ModSupport/comments/1t1fekj/redact_...)
log in, click on my profile, press f-12, go to console, run some script i found a while ago.
get to watch em go, one at a time. slow process compared to a API key but it's nice to see what I wrote 6 months ago and what the final karma score was.
probably gonna stop using the site in a month or so tho. site has gone down hill