Suppose dang edited your post to say "I like to get drunk at work", and there it is for the world to see. You never said that, but anyone looking at Hacker News would see:
"qup 10 minutes ago: I like to get drunk at work."
No, that's absolutely not OK! Now, consider that spez could just as easily edit some old Reddit comments someone wrote years ago to say something horrendous. Do you often go back to verify that all your old comments are unchanged? I certainly don't.
I have no way of knowing exactly which comments spez edited, or how significantly he changed them. And honestly, the not knowing is simply inexcusable. All we know is that he has tampered with the production database, not how often or how much.