Rabbi Avi Shafran, Agudath Israel’s spokesman, says this about pilegish:
While conceding that the practice is not a sin, Rabbi Shafran said “many things are permitted but not engaged in. This is not anything that is normative in the Jewish world. The definition of a marriage is between a man and one wife, like the first man and his wife.” He was referring to Adam and Eve.
Shafran is a fool. Abraham had a pilegish. Jacob had two. Throughout First Temple times, pilegish was normal, and it was commonly used after that until several hundred years after the Second Temple was destroyed. And, even after that it was still used.
I don’t write this to encourage people to go out and become or find a pilegish. But Shafran’s response is simply stupid.