Another thing to note is the DB.
Even though this is a more advanced version, fact remains that it simply conceals and doesn't erase, as erasing is impossible to do. He may be capable of erasing his chakra
signature, but he can't erase the chakra itself. As the DB states, to conceal his form, he uses chakra inflections, meaning chakra is still required to conceal form, and nothing indicates he conceals his form by other means, thus the Sharingan sees him.
It is perceivable with a dojutsu. Not to mention, Karin can do something similar [
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]. Also, when Kabuto is speaking about Mu in the VIZ, he claims Mu had "neither form nor chakra." [
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] Clearly, Mu has form since Contact sensing works on him, thus Kabuto was essentially speaking in a sensing manner, since you can't sense his form nor chakra, but should have no reason not to be able to perceive it with a Dojutsu.