I have absolutely no horse in this particular race. However, I do understand what the seller is saying about using terms such as "excellent", "mint", "very good". They mean all things to all people.
Whilst, I do not believe that there is an easy answer to this, I would like eBay to have proper guidelines to descriptions and one of the most "universal" methods (IMO) would be to have a scoring system, out of 10. With 1 being very poor, through to 10 being "new".
I repeat, this will not necessarily stop Sellers from abusing the system. However, it would provide buyers with some sort of quantifiable way of understanding the condition of clothing.
After all, if someone described a pair of trousers as an 8/10 (let's say "excellent" would be the descriptive word for this score), and the buyer got something what could be identified as a 6/10 (let say "good"), then it would be easier to "prove" the descrepancy.
I've purchased several items which have been described as "excellent", or worst still "mint", only for them to have obvious flaws (such as moth holes or tears).
I've also purchased items described as very good which have been like new.
eBay is a very difficult place.
I've been looking a mobile phones on eBay recently and would you believe eBay has a "New" category as well as a "New (other)" category. What is that about?
The amount of listings that use the latter to describe phones that they've been using for weeks or months is amazing and worrying.
So, I think more effort could be put in by eBay with enforceable "rules" for describing items.
Just my tuppence.