I don't see why being below-grade diminishes its value so greatly.

The real estate agent will play a role but technology will diminish their role and bring knowledge to the hands of the buyers and sellers.

I think we saw a shift in marketing approach perhaps a year or two ago as property values were being ignored or diminished for the sake of cashflow.

The court will order an appraisal of the property or properties that are to be crossed with the value of the property before the crossing and what diminished value there would be after the crossing.

While the solar warranty is for 25 years, the effectiveness of the solar will start diminishing over time.

The pool of risk taking landlords willing to rent to tenants with pets is diminishing.

Even if you go down the road of the math with your average daily balance and the effective rate on the HELOC, you're getting to the point of slicing hairs (reference:  Pareto Principle or diminishing marginal returns, your choice). 

Are there properties whose value would be diminished by strs?

I am debt free and it’s a wonderful feeling, unless ur goals are to seriously leverage and go realestate nuts as a passion or your income is going to diminish just pay it off and enjoy.

However, if the park is blighted or not in the path of progress then the values diminish considerably thereby dissipating the desirability and incentive to want to invest there.