The above quotes made me to understand that people still believe that your name has connection with your attitude
I want to say: "Of course!" to this. Unlike the name your parents gave you, you actually choose your forum nickname by yourself. Mine came out of a random name generator.You can't blame users from having different expectations from someone named "gunman" than from someone named "sensualbellax" for instance.
Quote
made me to wonder whether I will have a chance to prove myself and be comfortable in this forum. Having bad name doesn't mean one is bad please.
Here too: Of course 
Your nickname may give a first impression, but the rest is up to your actions. I've seen much worse nicknames than "gunman".As they say, "Don't judge a book by its cover".
They also say: "You only have one chance to make a first impression" 