The downside to talking to other people over the internet is that it's near impossible to tell when someone is being sarcastic or making a joke (unless they use an emotion such as xD or :V ). I forget about this sometimes and have to go back to change what I say. That being said, even I couldn't tell until you mentioned later in the post that "Person" was joking about their RP sample... I guess a lot of people (even me! xD) often forget that they are speaking through writing and over the internet, so even if something sounds like a joke in their head it might not come across that way to whoever reads it because they don't have the same voice in their head.
Don't worry, this wasn't you being ignorant or anything. I imagine anybody else would have reacted the same way, since to be honest "Person" didn't make it clear at all that he was making a joke. :U