Assuming Clippy can't owe paperclips (i.e., own a negative number), 0 paperclips minimizes his utility. So, I think the original sentence was OK, albeit overwrought.

Orthonormal is correct based on the very nature of 'utility'. The difference between 1 and 4 utility is three times worse than the difference between 0 and 1. Every single time and no matter what. That '0' or a minimum is involved is irrelevant. You cannot get diminishing marginal utility on utility itself.

The place for assigning extra importance to low values and zero is in the paperclip to utility translation and not the evaluation of how much you care about the utility.