When I use the term "two faced," here is what I mean. A person displays two opposing personalities, like being greedy on Monday and generous on Tuesday.
To a limited extent, everyone is like this. We are all complex people, and different traits come out under different circumstances. When a person's traits range from one wide extremes, with very very bad traits being balanced with very very good traits, that can feel particularly jarring to other people. People don't like that because very high expectations are being established before the crash.
Case in point, there is a game designer named Bill Coffin, a very proficient writer. To explain to hos fans why he no longer works for his former publisher, Kevin Siembieda, Bill wrote a very long and very detailed explanation of his history with that publisher. Bill called Kevin, "the most extreme case of Jeckel and Hyde personality I have ever seen in my life." Then Bill went on to describe how Kevin would be jovial, caring, charismatic, and generous to a fault -- but also a control freak, rageaholic, and paranoid when things were not going his way. Ultimately, Bill placed a portion of the blame of what happened on his own shoulders but decided at a very certain point that working with Kevin was just too stressful. Now, Bill edits magazines for a living and self-publishes games as a side gig. Although his work reaches a much smaller audience and he's no longer working his dream job, he's a much much happier guy.
To a lesser degree, two faced can also mean disceatful to me. I think that might be the intended meaning in this thread.