When it comes to non-discrimination, National Treatment gets most of the attention. But MFN can be interesting, too. Here's a passage from the U.S. third participant submission in the EC - Fasteners appeal:
24. A number of WTO rules explicitly recognize that, in the context of AD and CVD proceedings, products from one Member may be treated differently from those of another Member. For example, and as discussed above, Ad Note 2 to Article VI:1 of the GATT recognizes that dumping comparisons with domestic prices may not be possible in economies in which State interference is pervasive. Similarly, China’s Accession Protocol provides that a dumping comparison using costs or prices in China is not required unless and until investigated Chinese firms show that market conditions exist in the industry. Thus, various provisions of the WTO agreements provide for situations in AD and CVD proceedings where products from one Member may be treated differently from those of another Member, without contravening the obligation in Article I:1 of the GATT 1994.
What is the scope for treating different Members differently without violating GATT Article I:1? We may get some guidance from the Appellate Body soon.