Complex sentence: Nevertheless, the emphasis remains on one's personal verification of any teaching, and in particular whether a particular teaching reduces or eliminates the mental defilements of greed, hate and ignorance, or vice versa (in which case it should be rejected).
Split into simpler sentences: Nevertheless, the emphasis remains on one's personal verification of any teaching. More specifically, the verification pertaining to whether a particular teaching does indeed lead to the diminishment and non-arising of the mental defilements of greed, hate and ignorance, or vice versa (in which case it should be rejected).