So I have a use case where I chain multiple criteria together and it is possible that one criteria might contradict another. This is because thy operate independently.

So I might end up with a chain that looks like this:
Collection.not_in(:slug => ["some-slug"]).any_in(:slug => ["some-slug"])

Which produces:
<Mongoid::Criteria:0x1065f7808 @documents=[], @klass=Newsroom, @selector={:slug=>{"$in"=>["some-slug", "some-slug"]}}, @options={}>

If the criteria were added in a different order, ie:
Collection.any_in(:slug => ["some-slug"]).not_in(:slug => ["some-slug"])

Mongoid produces this:
<Mongoid::Criteria:0x1065cb370 @documents=[], @klass=Newsroom, @selector={:slug=>{"$nin"=>["some-slug", "some-slug"]}}, @options={}>

These two queries produce inconsistent results. I would think that they should produce a mongo query that is the equivalent of:
db.collections.find({slug:{$nin: ["some-slug"], $in: ["some-slug"]}})

which produces the correct result of not showing the item with that slug