Signatures are used on talkpages to easily track discussions, those participating in them, and who has which opinion about what. In the world of wikis, we call this having good "Wikiquette." As such, it is a direct violation of Wikiquette to include signatures on mainspace articles. For instance, if you noticed that an editor said Alduin's hair was green, when in fact, you know and have proof, that his hair is red, you could not edit the page and include your signature after the edit. Likewise, help pages and policy pages should be signature-free.