Not trying to be rude, but are you joking?
well, no. I guess in a situation like dren said, where it was cityrp or something, you might not wanna gain someone else's bricks like that, but if it's just a freebuild or something like that, who cares? I can't imagine any real issues coming from that
What defines a message that he'll reply to?
whether or not it's a message he decides to reply to. it's not like there's a solid criteria for it. it could depend on any number of variables, like his mood, whether or not he likes you, whether the issue you messaged him about was important to him, etc. nobody but badspot would be able to tell you whether or not he'll reply to a certain message