Are you sure your post was unwelcome?
Were you reporting an issue that was subsequently resolved by the changes?
Topics are routinely cleaned up so that users don’t have to scroll through hundreds of historical responses to get a grasp of the current situation. Forcing moderators to provide a reason for every removed post would be incredibly burdensome. official plugin topics (the topic you’ve linked is one of these) are very well-maintained, most have less than 100-replies apiece. Compare that to unofficial plugins, where many have hundreds of replies.
There’s also the possibility it was just an oversight. The team who do most of the moderation isn’t in a habit of deleting genuinely useful or actionable content, which is why I’m inclined to wonder if whatever you were asking for has since been addressed.