I used Power Delete Suite and you can set it to edit comments to whatever you want before deleting them. I recommend using something innocuous though as some subs have their AutoMod set to reject spammy looking stuff.

I’ve found that it didn’t work very well for an account that had thousands of years old comments though. I haven’t tried to run it again yet since this was just a couple of days ago but it did a good job editing and deleting newer stuff and getting everything on my less verbose accounts.

It was free and didn’t require giving your login credentials to some third party like shreddit and redact, so just depends on what you’re looking for.