If such a bug would be fixed, either StreamWriter or StreamReader should do something.

I can understand Doerwalter that it is somewhat not comfortable for a StreamWriter to detect whether these is already a BOM at current file header, especially when operating in append mode. But, IMHO, the StreamReader should be able to detect multi BOM during its life span and automatically ignore the non-first one, providing that a BOM is never supposed to occur in normal content.  Not to mention that such a Reader seems exist for a while, according to the "(extra unnecessary) BOM marks are removed
from the input stream by the Python UTF-16 codec" in bug215974 (http://sourceforge.net/tracker/?group_id=5470&atid=105470&aid=215974&func=
detail).

Therefore I don't think a WontFix will be the proper FINAL solution for this case.