The pile of poop would not ever get accepted as a character in unicode on its own. It's there because of including an existing character encoding set (IIRC fro

The pile of poop would not ever get accepted as a character in unicode on its own. It's there because of including an existing character encoding set (IIRC from Japanese featurephone messaging standards), which had a pile of poop character and other emoji, so for purposes of compatibility all the characters of that set must get Unicode mappings. So there's a situation of dual standards - all the weird characters that were included in any pre-Unicode text encodings for whatever arbitrary reasons are in Unicode and are always going to be there; but all the new weird characters need appropriate justification for inclusion and are likely to be denied.