You have to restart the app after changing it and wait a few minutes before reopening it, but I don't think this guy is really going to care because you have no idea where he lives and he obviously isn't going to tell you.

Also, when you post public threads on a forum site, yes people are going to reply to them, that's the whole point of using the forums.

Truth is, this guy is probably just casually saying these things and putting no effort, you are just wasting your time by doing all of this.