To use or not to use the Oxford comma  (serial comma)? It depends. In Canada, don't use it. In the USA, use it. But it's not that simple.

• The New York Times doesn't use it. 

• Curiously, Oxford University no longer uses it.

What is it?

Wikipedia explains, a serial comma or series comma (also called Oxford comma and Harvard comma) is a comma placed immediately before the coordinating conjunction (usually and, or, or nor) in a series of three or more terms. For example, a list of three countries might be punctuated either as "Portugal, Spain, and France" (with the serial comma), or as "Portugal, Spain and France" (without the serial comma)

Well illustrated in her book Eats, Shoots and Leaves, Lynn Truss of the BBC takes issue with poor punctuation.

• I think a comma should be used for clarification. Advice is that one must be consistent and that the use or misuse of it makes editors go to arms.

Two fencers

JOKE: A panda walks into a restaurant, sits down and orders a sandwich. After he finishes eating the sandwich, the panda pulls out a gun and shoots the waiter, and then stands up to go. "Hey!" shouts the manager. "Where are you going? You just shot my waiter and you didn't pay for your sandwich!"

The panda yells back at the manager, "Hey man, I am a PANDA! Look it up!"

The manager opens his dictionary and sees the following definition for panda: "A tree-dwelling marsupial of Asian origin, characterised by distinct black and white colouring. Eats shoots and leaves."