[member="Amanda Lori Ann"]
If they join a public thread, nobody will bat an eye if you join it too, gunning for them. Just make sure you cover all your bases. Some people love being hunted; some people actively hate it (but should get over it if they want to join public threads) so make sure your approach is unimpeachable. I recommend not attacking with your first post in the thread, and not using your first post to say you've already set a trap.