If you’re using a script to do so, make sure it’s handling API limits specifically for “edit” calls. I realized after I tried overwriting mine that it was quietly skipping a bunch of comments, presumably because there is (allegedly) a 1 edit call per 5 second rate limit. Since adding a 5 second delay between each re-write, it seems to be working for me.
I ran into this issue with u/j0be’s Power Delete Suite, I ended up writing my own script to do the job.
This, and also it’s far harder for them to revert if they decided too much of their content had been deleted by protesting users. Overwriting the content means it remains a persistent issue well into the future, rather than something they can easily ignore or undo.