Its just etiquette, if you say you are selling to one person, and arranging shipping etc, to then sell to someone else is wrong. I was looking at your other items, to make a larger purchase,but tbh I won't be buying from you. so you have lost out on other sales
And to be honest If I see who bought it, I'm guessing they sent you a message saying they pm'd you on this thread. I won't sell to them in future either. Which is a shame as most of the cocker fans frequent the same forums etc
Yes you can sell to who you wan't but the rules are put in place for your protection.