Before Alaiyna B (Faith) closed down the sales of her bath and body products, she was recommending and selling syndet shampoo bars. She also has this prominent warning on her blog:That's why I worded it the way I did, Zany. I qualified it by saying some can use it but it isn't recommended. The fact that the pH is too high is just that.... a fact. Not wanting to start an argument but just wanted to point out to a new liquid soapmaker that it isn't recommended even though some, like you, can and do use it without issues. This is not the place to get into this discussion. It's been written about many, many times and if the OP wants to look it up, she is more than welcome to delve into the fray. Just not here. And, incidentally, I grew up using soap based shampoos because it was cheap. My hair did not like it.... at all.
As far as using liquid soap as shampoo - please note that not all hair types can handle high pH cleansers. High pH cleansers will lift the hair cuticle/shaft and all those tiny pieces of hair can get very tangled and damaged in the process as you massage and manipulate the lather throughout the hair. Lower pH conditioners can be used afterward to close the hair shaft but if you have damaged your hair, it will not reverse the damage. No, you cannot lower the pH of liquid soap to be neutral or acidic and closer to the pH of your hair and scalp.