Uhm, your case is similar to this one:
https://cit.gg/index.php?topic=356095.0.
If you weren't trolling his board by offensive/unacceptable words then he has no right to edit it and write whatever he wants to. Probably that's a misuse for his moderation tool. Otherwise, if you attempted to troll his board then he has the right to edit your post or even delete it.
But as I see, you said " Good luck " which is acceptable so you weren't trolling, and many other people already have said that so. Yet, if you are not comfortable with what he has written. You can submit a complaint against him.