Nick,
There is no such thing as pH negative, all PH's are positive apart from 0 and we won't see any of them in cleaning solutions.
Basic chemistry does not suggest that two solutions mixed together become something else, this would only occur if a chemical reaction takes place.For example alcohol and water mixed together are just alcohol and water mixed together ,not a new compound as they have not reacted.
Leaving aside the 'science' I am more interested in what results people are finding in practice , afterall most of us have only been fresh water rinsing for a short time and when experienced CC,s say they are adding detergent to inhibit resoiling , I for one take notice.
So come on guys what are your real life experiences , I have been suprised when I have returned to places , where I have used a fresh water rinse , how dirty the carpet looks.
Cheers,
Doug