Does Esperanto have a governing...
body which controls what is and isn't official in the language?
La Akadamio de Esperanto is a group that doesn't control what is and isn't allowed to be said by Esperanto speakers but describes what appears to be common usage and recommends words and expressions that it sees as having come into the Esperanto community to a point where they will be understood generally throughout the whole community. The original 16 rules must be followed; otherwise, new expressions that develop naturally in the community to a point of sort of critical mass are looked at. The community of speakers, in effect, controls what is and isn't official in the language through usage and having regard to the 16 rules.