Delete all your comments in reddit, navigate to https://www.reddit.com/user/{YOUR USERNAME}/comments, and reload. Only compatible with old reddit interface. Switch to old interface before using.
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Thanks for your suggestion! Will update the script accordingly.
When writing the script, I switched to old interface using reddit setting. So the url stays www.reddit.com.
Works great but one change made it more straight forward.
Change line 4 to: // @match https://old.reddit.com/user/*/comments
I changed the star to my username but I don't think that is necessary. I then navigated to https://old.reddit.com/user/{USERNAME}/comments and boom comments gone. Hope this could help someone!