Idk how we could do anything about preventing a pre, since a pre isn't a pre until someone with a retal follows up.
Not only that, but there's many legitimate attacks that aren't really pre, but look like it due to chance. It's very plausible you just happen to get attacked and then retaled by someone else, totally unrelated.
So realistically, there's nothing that can be done about a "pre", since it doesn't literally exist. It's just a regular attack.
Which was where my idea about a new kind of "castle protection" comes from, how we can manipulate the logic to bust the effectiveness of getting attacked + retaliated, whether by chance or strategy. But it's complicated since we don't want to encourage castle passing as a way of gaining castle protection, and also don't want to leave the guy with a legit retal to be prevented from getting their castle back.