To quickly answer the question, no, soft water cannot be too soft. If by too soft you mean, whether or not the water can be softened to a “degree” that will hurt your skin or well-being in any way, then the answer is still no.
Water softeners are great, but they also raise some questions whose answers are not too obvious.
Getting rid of all of the hardness in your water is good. As a matter of fact, it is very healthy, but it feels quite unnatural. This is so because your skin is not used to the feel of soft water.
It is no secret that we have been conditioned to hard water. This is not a conspiracy, but hard facts related to the molecular levels of water that run through our pipes. Water that is too high on dissolved minerals, such as calcium and magnesium.
To recognize hard water, next time you wash your hands with soap (I hope this is every time for you), see if you feel a film of residue left on top of your skin. This is what hardened water feels like.
Soft water, on the other hand, will give you that slimy feeling that you are not used to. It might even be considered kind of awkward at first.
What helped me, was to think of soft water on my skin as moisturizing and healthy, which it is. Rather than, think of it as slimy and too soft.
This is not to say that installing a water softener will save you a whole lot of money on expensive lotions. But, you can certainly enjoy some natural silky smooth skin for less money.