This site uses as the primary spelling for names that are commonly found in English speaking countries the form normally used in the United States and English-speaking Canada. You will almost never find any diacritical marks used in names in the United States. So the original French spelling of Noel would be Noël, but almost every man in the USA or English speaking Canada who has the name would not use the mark, and probably doesn't even realize that the mark is necessary in French.
In French the name would be pronounced in two syllables. In the USA it is normally pronounced in one syllable, rhyming with "goal" or "hole".