User:Asithol/Proper use of the comma

Why, oh why, do so many people not know how to use a comma? I am a pretty active reviewer on the GAN page, and rare is the article where I do not have to fix multiple instances of failure to use commas properly. To be honest, I'm a little perplexed by this, seeing as how it's really not that complicated. What follows is a guide on how to properly utilize commas in writing. This is not meant to be an exhaustive guide that covers every little obscure rule (of which there are several), just a basic tip sheet on the most common situations and errors in encyclopedic writing.

Joining two thoughts
This is, by far, the most common error. When joining two thoughts into a single sentence by using a conjunction, a comma should be used only if both portions of the sentence can stand alone (and make sense) as complete sentences. Let's look at an example:
 * "The Melida leader informed the Jedi that headquarters was a weapon-free zone, and that they would have to leave their lightsabers outside."
 * Wrong. At first, it appears that the comma is correct since "They would have to leave their lightsabers outside." is a complete sentence, but let's look closer. There is another word&mdash;"that"&mdash;immediately after the conjunction ("and") that must be considered. After including the extra word, the second part of the sentence comes out as follows: "That they would have to leave their lightsabers outside." This makes no sense and cannot stand alone, as it relies on the first six words of the main sentence, and therefore no comma should be used.
 * "The Melida leader informed the Jedi that headquarters was a weapon-free zone and that they would have to leave their lightsabers outside."
 * Correct.