Dear Sir
Thats really an interesting question and I wasn't aware of it that they were merged.
Infact, I believe IT IS WRONG TO MERGE THEM. It has actually been merged by one Nepali guy B.B.Raskoti, if you know him. He is currently working in China with Prof. Jin Xiao Hua. Even Dr Andre Schuiteman from Kew was co-author, but both of them are currently out of station so I will wait for a while to write to them.
BB.Raskoti has created many new species from Nepal which is absolutely wrong like Gastrochilus nepalensis which is Gastrochilus affine to me. Then Bulbophyllum nepalense which is actually Bulbophyllum retusiusculum and I had this plant in my garden. When I told him about the mistake his answer was, PLEASE STUDY THE ORIGINAL SPECIMEN PROPERLY. Infact I think it was he who should have studied properly and not me. I already have lot of work (I am already on the verge of completing one article where I have merged 23 names into other 17 names) so if you or any other member are interested they can write an article to merge the above two species. But one task would be to find these two. Once Dr. Andre and Prof Jin are back in office I will ask them about your plant.
I am copying this to some members who can help you write these articles and of course I will help you.
For the time being you can keep your Peristylus duthiei as it is (which to me is correct or it can be changed to Herminium duthiei but not to Herminium josephii).
I am adding Dr. Jeewan here too because I assume he has seen Peristylus duthiei, Herminium macrophyllum and Herminium jospehii live in the Himalayas. I am also adding Dr. Ishwari here because he found Gastrochilus affinis in western Himalaya recently.
I will publish my next round of new synonyms may be after 6-7 months, so you guys have time to work on this.
Thanks and regards
Pankaj