This is slightly different than account deletions. They’re also restoring individually deleted comments.
I, for example, deleted every comment I ever posted on Reddit, but left my account itself in place. As of this morning, many of my comments appear to have been restored.
I checked my profile by visiting old.reddit.com/user/[username]/comments.
Then I used shreddit to edit/delete my comments, and kept viewing that page to confirm comments were being removed. I also picked a handful of comments and confirmed they appeared as “deleted/removed” in the threads in which they appeared.
When shreddit was done, I checked my profile comments list to confirm it was empty. I double checked 1 and 12 hours later in case there was some cacheing.
But people here are saying not all appear on the profile pages. I've checked mine and indeed there are a handful of undeleted stuff. My last purge was before the blackout and I'm sure it was completely clean as I had to do a couple more passes to catch all the sumbission/comments that for some reason weren't wiped (edited & deleted) on the first pass.
I also use old.reddit but I believe on the new.reddit you can limit a search to only a defined user comment. Maybe with some wildcards or regex one can get to them? Otherwise you'd need to know of a submission or a direct link to your comment.
I, for example, deleted every comment I ever posted on Reddit, but left my account itself in place. As of this morning, many of my comments appear to have been restored.