How to report harassment taking place within Battle.net chat (mobile or desktop)
How to report a player for cheating in Diablo III
Reporting your own behavior won't prevent action.
How to report players in Diablo III.
Information on how to report forum posts
Reporting an Exploit or Hack
How to report a player who is threatening with harming another person or a place
Reporting another player that is using an offensive or inappropriate BattleTag
Information regarding harassment for streamers
How to report another player