Quotes are not uneditable… but neither are comments.

You kinda get into an ouroborus of who has fewer edits, and honestly I don't know how to solve for that, but I do know that if you had substituted "n-word" for the slur it would look exactly the same if the OP edited the comment after the fact. Quoting the slur doesn't mitigate that.

“Zero tolerance” becomes a problem when the system requires you to quote, but then some months or years later decides to change the rules and applies them retroactively. I

Any policy becomes a problem at that point. It becomes less of a policy and more of a guideline