(Resending.  I suspect it didnít go through because I wasnít subscribed yet when I sent it.)
This is an issue concerning the YAML 1.2 specification <http://yaml.org/spec/1.2/spec.html>.
This specification is intended to ensure JSON compatibility.  But one thing about JSON was left silent: the behavior of character-escaped surrogate code points ("\uXXXX").  According to RFC 7159, the latest JSON specification, a pair of character-escaped surrogate code points is converted to a supplementary code point under the UTF-16 rules (see the last paragraph in section 7, Strings, in RFC 7159), while this is not mentioned at all in YAML 1.2.  For JSON compatibility, this behavior ought to be used in the YAML specification.