Expletive "ne" following a positive main verb

My answer to a quiz question in which the main verb is positive included the “ne” expletive in the subordinate clause following "sans que". This was marked as wrong. I’ve followed the discussion about the use of this expletive with “sans que” and there appears to be no consensus about whether it can be used or not when the main verb is positive, and even the Académie Française equivocates. It seems that it’s quite common for “ne” to be used in this context, in which case shouldn't "ne" be allowed whether the main verb is negative or positive?