On "nothing to worry about."
That is not necessarily true. Many scam artists pose as door to door sales men. The info people are willing to provide is often times quite valuable to them. Others seek to case the joint from the door, deciding whether it is worth their time to visit when you are away. Still others seek to distract you while others attempt to steal what they may elsewhere on the property.
But yes it is true that most are merely involved in sales, trying to eek out what they may.
Meriam Webster's: Main Entry: ci·vil·ian Pronunciation: \sə-ˈvil-yən also -ˈvi-yən\, Function: noun, Date: 14th century, 1: a specialist in Roman or modern civil law, 2 a: one not on active duty in the armed services or not on a police or firefighting force b: outsider 1, — civilian adjective