I have uninstalled the extension and script (at least I hope I have). Sorry if this is not the right place to post this. I would think it's safe, but I also know that I let my emotions get the best of me and did install a scripting program in my browser. The code is open source and has been used by thousands of people. I installed the extension in an entirely new windows profile and plan on deleting the profile later tonight since it's only purpose was to delete messages on a old discord account I don't use. Now I have a new fear, that what I installed might have been a keylogger or won't uninstall or. My fear of getting these messages deleted overshadowed my fear of having my old discord messages stay there forever.
I know that running scripts could be dangerous and that it would pose a threat.
I don't know much about browser extensions or code. I wanted to delete all my discord messages and ended up using a 3rd party tool to get the job done. For some context: I created a new windows profile and installed tampermonkey and a following script to that browser.