There are several ways. If you want to overwrite and delete:

https://greasyfork.org/en/scripts/10905-reddit-overwrite-extended/code (This runs as a script in your browser over a plugin, like Greasy Fork, you install the JavaScript Plugin, add the script code, navigate to your comments and let it work).

For just overwriting without deleting.. haven't found something good yet. I adapted the script above for it and it took a while.

There is also shreddit, but it has more setup: https://github.com/x89/Shreddit