Greasy Fork is available in English.
Creates the option next to edited and deleted Reddit comments/posts to show the original comment from before it was edited
< Unedit and Undelete for Redditについてのフィードバック
Glad you like it!
For libreddit, it would require a major update due to the layout being different, but also it seems like it's not even possible due to their Content Security Policy which will block all outbound external requests. So unfortunately I can't help with that.
Thanks for the script. Can you add support for alternative reddit frontends, in particular (https://libredd.it/). I tried adding the domain in the beginning of the script, but it didn't work.