The conflict of opinions is due to the fact that some speakers see 'use' as an auxiliary verb and others see it as a lexical verb. ' and 'It usen't to be allowed'. If you dislike those, as I do, then stick to the lexical verb choice.
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SiernanI don't understand why the alternative with 'd' is also givenThat alternative is given because so many people use it that way. It is a description of what people use, not a guide (or prescription) for what you should use.