Note on title casing in set_headers

h11/_headers.py

@@ -206,6 +206,14 @@ def get_comma_header(headers, name):
 
 def set_comma_header(headers, name, new_values):
     # The header name `name` is expected to be lower-case bytes.
+    #
+    # Note that when we store the header we use title casing for the header
+    # names, in order to match the conventional HTTP header style.
+    #
+    # Simply calling `.title()` is a blunt approach, but it's correct
+    # here given the cases where we're using `set_comma_header`...
+    #
+    # Connection, Content-Length, Transfer-Encoding.
     new_headers = []
     for found_raw_name, found_name, found_raw_value in headers._full_items:
         if found_name != name: