The art of polite replies and comments can be hard to master, and for some it comes more easily than for others I think. It is hard at times, but it can be learned and practiced, so one can become good at it even if it takes time :-).
In regards to this comment from Loutre I think wasn’t mean bad, but came across as more passive-aggressive than intended.
I approach would probably be something like this:
I am sorry to hear you are considering leaving the game over this, if you want to quit or take a break for a while after this indicent I understand.
We also appreciate the feedback in regards to that we should try to be more clear in terms of a heads-up before banning in the future, whether it be short bans or permanent bans.
Even if not the second part and just the first part I think sounds more polite, but yeah any thoughts on this approach?