I did a search for this topic and one of the posters who claimed that the case was responsible for scratches on his phone stated that he had modded his case. What likely happened is that the sharp edges of the plastic from his mod is what scratched his phone, not the original design of the case itself.
As I've already stated, this thread is inherently stupid and biased since the posters are completely ignoring the testimonials which report zero damage and perfect protection over months and years of use. And these testimonials are far easier to find than the reports of damage, which seem to be concentrated in OCD fan sites such as this forum.