Really, both of you are correct.
Keykeeper, it is a designation. If you go to buy one new you would get the one you want by telling them right or left.
And, I know that you are largely self taught, but like I said, there is a method of using a cross pein thst makes it the best tool for the job. As a self taught person, who is very passionate about smithing, you have an opportunity to find out what this method of using a cross pein is. You may even like this method.
The use of handedhess in this tool has to do with ergonomics and how you can see the work. Here is my best (although silversmith) explanation. (I welcome correction. I only claim 85% accuracy, and my life has been a series of course corrections. Constantly adjusting.)
If holding a piece with your left hand, with your arm held a natural way your fist in front of your you and lined up somewhere in the vicinity of your centerline, the pein lines up straight in front of you.
Here is my rough drawing (excuse my art, I am an engineer, after all)
Dimensions are to scale (measured off of me. I just ate, by the way. Nevermind the last one, Mrs. Chillly says I am a little thicker.)
The fact that any tool can be used in other ways does not affect the truth that there can often be, sometimes a little less obviously, a very good method for which the tool was intended. This is one of those. The double cross peins are simply made for everyone. You can imagine that lefties are rarer.
I think that both keykeeper and twilight show great knowledge and passion about smithing. I for one, would like to see some of their work. I imagine it is pretty cool. And, hey, we haven't seen any if Branson's work lately, have we?
Sincerely,
Chilly
Edited to add the following picture: