Please find the supportive links and research documented on the Wikipedia page regarding the correct name spelling of the city of Pétion-Ville.
The conclution of the research on the name spelling on its official Wikipedia page: https://en.wikipedia.org/wiki/Talk:P%C3%A9tion-Ville#Spelling
"the results used by Haitian officials, the occasional use in circulars and the fact that our English encyclopedia assumes foreign spellings at times, may just be enough to narrow out WP:COMMONNAME in favor of Pétion-Ville"
Another supportive document:
The "Office des Postes d'Haiti" (Haitian postal office):
126.96.36.199 14:09, 9 February 2017 (EST)