Ah, the comma
Commas. They're a very versatile little punctuation mark. They lead a double life, sometimes imparting syntactic meaning and sometimes semantic. They can distinguish an integrated (restrictive) from a non-integrated (nonrestrictive) clause or apposition, they can separate clauses or phrases in sequences, and they can distinguish vocatives from subjects or objects. (All of this in writing, obviously.) They have a lot of optional uses, and a lot of mandatory ones, which means that sometimes when you leave one it it's no big deal ... but sometimes it is. As in this Non Sequitur from yesterday:
Now, it's true that Eddie is at the moment Flo's lone customer. And I don't at all doubt that he's hygenically challenged. But given the kind of place she runs, I sincerely doubt he's ever her "lone hygenically challenged customer".