Doug,

What you seem to be saying is that softened water may contain between 0
and 200 mg. of sodium per liter I'm ok with that. Then say that softened
water makes bad coffee but you don't tells us whether it's the sodium and
how much sodium concentration makes the coffee bad. That doesn't work for
me.
I have a softener because my water contains about 35 gpg of hardness,
probably calcium. I do make coffee and tea with the softened water. It's
fine for this, in my opinion. The unsoftened water makes terrible tea,
there's a precipitate.
Explain how much sodium is required to produce your bad coffee. My
experience argues that some sodium is ok.

Dave M.