Remarks on good vs. bad characteristics in vertical differentiation

In a recent paper, Garella and Lambertini [Economic Letters 65 (1999) 245] claim that we should distinguish between good and bad characteristics in analysing the incentives for a duopoly to vertically differentiate their products. We prove here that the results obtained by the authors are false and we show that in the context of their model, maximum differentiation should appear whether characteristic is good or bad.