if you'd take a close look at the following lines accepted as part of the patch for stripping out unwanted/non standard cookies over trac:

+                try:
+                    old_set(key, real_value, coded_value)
+                except CookieError:
+                    bad_cookies.append(key)

then you will find that trac actually behaves just like what is requested in the "original" RFC, namely that the colon is part of the reserved or special characters not meant for inclusion with the cookie name or, as it was stated in the referred rfc, the token.

Please do not fix.