This page explains the conflict between Harold and Duncan.
Conflict[]
Harold and Duncan were never friends, mostly enemies and it carried onto TDN4. In the Day 1 Pre-Chat, Duncan asks Harold why he's here and says that Harold has no skills. Harold then replies by saying why Duncan was invited, which Duncan remarks that wasn't a very good introduction. Then in Voting Votes for a Vote, Harold voted Duncan stating that he would get his revenge. In his speech he completely dissed Duncan, saying bad things about him and that he is happy he's gone.
Signs of Friendship[]
Harold and Duncan agreed that Chris and Frank hosting is dangerous.