Reply to No Such User's Opinion 
Not sure if you're able to comprehend, but here are few facts to consider
Serbia was a country during Selimović's life for 19 years before Yugoslavia was (1910-1918 Kingdom of Serbia, 1918-1929 Kingdom of Serbs, Croats and Slovenes, 1929 SCS was renamed Yugoslavia)., And it was also one of the Federal Republics of Yugoslavia. This is why on the Yugoslav censuses, "Serb ethnicity" was an option, which Selimovic selected. 
The majority of the members of the Partizans and the Communists were Serbs, being a Serb and being a partizan/communist was not mutually exclusive
Your implication that he changed nationalities from Bosnian to Serbian to spite Sarajevan "harrasment" is ridiculous because he was not addressing his nationality in the letter, but rather his ethnicity, which is an unchangeable characteristic.
The Serbian language's standardization was devised by Karadzic in 1818, 17 years before the Croatian latin alphabet was standardized by Ljudevit Gaj, and 32 years before Serbo-Croatian was devised at the Vienna agreement. If you read Mesa Selimovic's books you would know that the modern standardized Serbian language is older than both modern standardized Croatian and Serbocroatian as he wrote a book discussing Karadzic's reforms. Also there are Croatian and Serbo-Croatian dialects that are not mutually understandable with the modern standardized Serbian that Selimovic wrote in, namely Cakavian and Kajkavian.
You say Biographies are reliable sources. Then read this excerpt from Selimovic's own autobiography "Sjecanja" that he wrote himself and you will find the following quotation: "Potičem iz muslimanske porodice iz Bosne, a po nacionalnoj pripadnosti sam Srbin. Pripadam srpskoj literaturi" -> TRANSLATION: I COME FROM A MUSLIM FAMILY FROM BOSNIA, BUT BY ETHNICITY I AM A SERB. I BELONG TO SERBIAN LITERATURE
You are clearly not a "sane and neutral editor" if you call me a bully and tell me to fuck off simply for adding relevant (the author's works deal primarily with ethnic questions in the Balkans) additional information and citations from the author's own autobiography to an article.