By Elizabeth Culliford (Reuters) - Live-streaming service Twitch will ban users for offenses such as hate-group membership or credible threats of mass violence that occur entirely away from the site, in a new approach to moderating the platform, the company said on Wednesday. The Amazon Inc-owned platform, which is popular among video gamers, said under its new rules it would take enforcement actions against offline offenses that posed a "substantial safety risk" to its community.