Well, the way I would put the answer would be "Well, DUH!"
I'm serious, two likable people, seeing each other every day, eventually, you begin to see good things in the other person, and eventually, start to think that a romantic connection could happen.
That's how relationships begin afterall, you first become friends, then lovers.
The thing that prevents such things, or you hope would prevent such things, is when the two people are ALREADY involved with someone else.
It makes one wonder about the life of that reviewer. Are they in a disfunctional relationship where one person is an unlikable character? Has that person never had a friendship with a person prior to falling in-love? Have they never fell in-love at all?
I am a likable person, and so is my husband. Had we met because we had a project to do together, I could see myself becoming friends with him in that setting, and then falling in-love, in time. Because, afterall, we met, became friends, and fell in-love.