Delete chat through user history
/clear works for non-moderator viewers but for mods, we can still view user chat histories. However, testing commands clutters chat history and it's really not nice to look at.
A separate option for a broadcaster to completely wipe their channel's chat history or to delete chats from a user history would be cool. The latter option would help in channels where chat moves too fast for a moderator to scroll back in order to delete a message.