Reddit said years ago that they keep the content of deleted comments, but editing overwrites the content in their database, that is why these extensions were written.
They must have changed it or been lying from the start. (Reddit was partly open source waaayyy back in the day, so one could go check)
Or they're conveniently considering the use of those extensions as an ongoing cyberattack (they probably go against ToS, at the least), and use this opportunity to test their ability to restore from backups.
Honest question: How young are you? This reads like someone who's very young and naive learning for the first time how the digital world works.