It's common but I always laugh when I see a seller in his sales thread that says, "this is how it's going to be" "Not my problem" Blah blah.

I have no problem with the rules they're setting, but with the way they're saying it. Do they realize that they sound like jerks that people may not want to deal with?

Take a hint from me, and try some social etiquette. As an eBay powerseller and someone who sells tons of watches on here, a polite thread is always better. Hell, I even throw a "thanks for looking" at the end of most if not all my threads..