I'm glad you started a thread on non-duality. For the past nine years I've lead a group that studies the Buddhist Discourses. Recently some participants brought up the non-dual view in a way that implied that Buddhism shared that perspective, as if everyone knows that to be the case. After this happened a few times I offered that I was not a non-dualist. My view is that one can interpret the Buddha's teaching in a non-dual way, but there is nothing that compels such an interpretation.
For the past 20 years or so there has been a wave of non-dual teachers in the west; I refer to them collectively as 'western advaita' because I think in crucial ways their presentation of advaita differs from the Indian version of advaita based on Shankara's teaching. This wave of teachers has been very successful. So much so that it is now widely assumed that non-dual teachings are superior to those that are not non-dual. For example, if person N presents a teaching, and person M says the teachings is dualistic, the response of N, in defending the teaching, will be that it is not really dualistic. N will not respond by saying something like, "So what?" because nearly everyone now accepts the idea that non-dual teachings are superior, the pinnacle, and the ultimate.
I think this assumption of the superiority of non-dual teachings is unwarranted. There are great, and very articulate, spiritual traditions that are not non-dual. Christianity is one of these , Platonism is another, Confucianism is yet another, and there are numerous other traditions that are not world-wide, such as Shinto, that are not non-dual teachings. In addition, most Hindus are not non-dualists and there has been a sustained critique of advaita in Hinduism that I find articulate and worth examining. The Jain teaching is also not non-dual and has successfully resisted and critiques advaita. I would also suggest that the Buddha's teaching is not an example of non-dualism, at least as non-dualism is presented by western advaitans.
Non-dualists tend to ignore the great difficulties that non-duality has as a coherent presentation. First among these is the problem of evil. This difficulty is not confined to advaita (dualists struggle mightily with this topic), but it has a special undermining effect on advaita for if there is really only one reality, without a second, then why is it that evil exists in the world, for if there is really no second, and evil exists, then that would imply that the one reality is evil. To get around this advaitans argue for the illusory nature of appearances and the mind-made nature of ethical judgment. But if appearances are illusory then how is that they can say that appearances are illusory; that is to say they seem perfectly content to use illusory appearances to make their case, thereby relying on the efficacy of cause and effect, when it suits their purposes, while denying that efficacy when it suits different purposes.
A second problem is the problem of manyness. The world of appearances does not support the idea that there is ONLY one reality. If one goes along with advaita that there is only one truly real thing, or essence, or being, then why is it that the world of appearances is differentiated? Whence comes differentiation? Dualists do not have a problem with differentiation. Buddhists do not have a problem with differentiation because it is simply a manifestation of the causal nexus at the heart of Buddhist understanding. But for advaitans differentiation represents a constant presence which undermines the core of their world view.
There are other difficlties facing advaita, particularly western advaita, but I don't want to write a long essay. Again, I appreciate you raising this issue as I think western advaita has been given a free ride for far too long.