FIXES:- Followers would sometimes rejuvenate items they had in their inventory.
Those actions can influence your reputation, increasing it for some factions and decreasing it for others.Killing a critter (See below). It won't raise your reputation above 0.Joining an official faction (NPC-Driven : Vault City citizen, Navarro, Raiders...) : See the main article about it, Reputation changes when joining an official faction.Joining the Slavers.
(source)This might help a bit, Shangalar.