Board Thread:Theories/@comment-32129965-20170528032910/@comment-1327106-20180816184010

There are quite a number of people who like Jean. He can be a pain in the butt, but I like him specifically because he's the person who voices the unpopular opinion. When Armin and Mikasa want to trust in Eren (speaking about earlier points in the story), he doesn't. When Marlowe wants to be gung-ho about joining the Corps, Jean is the one who brings him down to earth. He's the truth teller of group and every cast needs somebody who's willing to be the voice of argument. A lot of times, Jean is that voice.

Maybe you don't like that kind of character, but they're definitely not useless and tend to be helpful tools for authors. Unsurprisingly, Jean was Isayama's favorite character for a while precisely for this reason.