[sfnt] Comment improvement.
diff --git a/src/sfnt/sfdriver.c b/src/sfnt/sfdriver.c
index 460fc9e..9f7a327 100644
--- a/src/sfnt/sfdriver.c
+++ b/src/sfnt/sfdriver.c
@@ -464,7 +464,12 @@
typedef int (*char_type_func)( int c );
- /* handling of PID/EID 3/0 and 3/1 is the same */
+ /*
+ * Handling of PID/EID 3/0 and 3/1 is the same. The language ID
+ * restriction to use value 0x409 (US English) comes from OpenType's
+ * recommendation section
+ * (https://docs.microsoft.com/en-us/typography/opentype/spec/recom#name).
+ */
#define IS_WIN( n ) ( (n)->platformID == 3 && \
( (n)->encodingID == 1 || (n)->encodingID == 0 ) && \
(n)->languageID == 0x409 )
