Naïve, naïf, naïvety, naïveté

I have two related questions about the word "naïve" and its relatives. The first is, shouldn't it be "naïf" if the subject is male? I've been told that it's correct to use the correct ending of foreign words when applied to objects in English with determinate gender (i.e. people).

Second, if not, is the diaeresis absolutely necessary? If "naïve" has become an English word, is the accent still compulsory? (I'm sure there are examples of foreign words whose accents have atrophied away as they become English words)

Third, should the noun from "naïve" be "naïvety" or "naïveté"?

Solution 1:

The New Oxford American Dictionary reports that the meaning of the words is the following:

naive /nɑˈiv/ (also naïve)
adjective
(of a person or action) showing a lack of experience, wisdom, or judgment: the rather naive young man had been totally misled.
• (of a person) natural and unaffected; innocent: Andy had a sweet, naive look when he smiled.
• of or denoting art produced in a straightforward style that deliberately rejects sophisticated artistic techniques and has a bold directness resembling a child's work, typically in bright colors with little or no perspective.

naif /naɪˈif/ /nɑˈif/ (also naïf)
adjective
naive or ingenuous.
noun
a naive or ingenuous person.

It is true that the first word derive from the French word that is the feminine word of naïf, but from the dictionary I get they have different meanings.

• naive is used only as adjective.
• naif has the same meaning of naive, but it means also ingenuous.

Solution 2:

Since English generally does not have many gender specific words, insisting on them with foreign words may be a lost cause. As for nouns, fiancée and fiancé are used, but many gender specific nouns are being dropped in English. Mailman is replaced with letter carrier, actress with actor etc.

Accents are usually only used when the foreign look is appealing or when mispronunciation would result without one.

Solution 3:

I've been told that it's correct to use the correct ending of foreign words when applied to objects in English with determinate gender (i.e. people).

I'm suspicious about this. It sounds like hypercorrectness or whatever the word is, generally trying to come across as high-falutin'.

Second, if not, is the diaeresis absolutely necessary? If "naive" has become an English word, is the accent still compulsory? (I'm sure there are examples of foreign words whose accents have atrophied away as they become English words)

This is where you need to reach for the reference books. For example, the "Oxford Writers' Dictionary" gives naïve as the correct form. Incidentally it also says not to use "naif".

Third, should the noun from "naive" be "naivety" or "naivete"? (with an accute accent)

According to the Oxford Writers' Dictionary, "naïvety" is right. But then after that it gives naïveté as well.