Often times I chat with people in this site. I open up with greetings like "Hello there :) care to chat? :)" then wait and hope for a reply. When I do this, I'm expecting some sensible and good conversation from my respondents. However, when I try to send a message again, that's when I find out that they've already blocked me. And this happens very often.
I'm not demanding anyone to reply and engage in a conversation with me. But, if you're not interested, then a simple, "Sorry not interested" would do to take away the burden of waiting for a reply. I'd very much prefer this than just blocking your respondent right away. I've always been courteous with how I chat with people here. But, as it seems, I can't expect the same from most of them.
