First of all, I think that's a very complex question that is perhaps better addressed by a lawyer. I'm a public policy professional, not a lawyer; however, I'm happy to speak briefly to it.
My understanding, from speaking with our lawyers and given the way the Canadian system works, is that the phrase “gender identity” would be interpreted by the courts to include the expression of that identity. That would be in line with the Supreme Court's repeated statement that “a broad, liberal and purposive approach is appropriate” when interpreting human rights legislation. From that perspective, I suspect that we would be on good legal grounds with just “gender identity”.
However, I would be concerned that it does create some ambiguity, given that this leaves it up to the courts and we cannot guarantee that such would be the case. I would also be concerned as to what signal it would send if the committee were to remove it. In future cases, if the courts were to look at that as a signal that gender identity shouldn't be included, or if were not Parliament's intent, that would create a large concern for me.