How to delete all reddit comments before deleting your account (Chrome)
If you'd like to sanitize your account before deleting it I use this method. I use chrome on W10 and I'm not sure if it works with other browsers or OS.
To make this work you'll need to be using RES on desktop. Go to your profile and load up all your comments and submissions, I just hold down spacebar until everything is loaded. Once that's done I do the above command and the comments/submissions get deleted one by one.
EDIT: Looks like there's easier/faster ways to do this so go with what works for you.