What is meant by unchastity is the taint in a woman?
IMO &quot;woman's stain&quot; is a mistranslation (or at best gives the wrong impression).
The whole chapter (of the Dhammapada) is about ways in which the audience (e.g. you or me) may be stained (or are stained, were stained).
(It would be applicable to &quot;a woman&quot; only if she were the reader, the subject, the audience of the talk -- but in the AN 8,15 context, at least, the audience was all men, all bhikkhus).
I think that (i.e. that it's the audience's stain, or that the audience would be stained if they were blame-worthy) is evident from the context -- for example from the start of that chapter of the Dhammapada:


One by one, little by little, moment by moment, a wise man should remove his own impurities, as a smith removes his dross from silver.


... through to the end ...


Easily seen is the fault of others, but one's own fault is difficult to see. Like chaff one winnows another's faults, but hides one's own, even as a crafty fowler hides behind sham branches.

He who seeks another's faults, who is ever censorious — his cankers grow. He is far from destruction of the cankers.



It's meant as advice to you ... and is not a statement that's meant to censure &quot;a woman&quot; (itthiyā).
Similarly you may be stained by ...

Your being lazy in the presence of beauty
Your having a house and being negligent (or, possibly, being negligent because you have a house)
Your misconduct with a woman

The Pali (Malitthiyā duccaritaṃ or malaṃ itthiyā duccaritaṃ) doesn't have all the prepositions which translators add to the English (at most the Pali nouns are declined, have a case ... I think itthiyā is declined like jāti, for what that's worth, so the syntax doesn't distinguish whether it's genitive, locative, dative, ablative, or instrumental; there's no verb).
I think the word-order in the Dhammapada is unreliable (it's highly condensed, to make it verse); but that the word-order in AN 8.15 i.e.

malaṃ, bhikkhave, itthiyā duccaritaṃ

... implies that the word itthiyā is there to qualify the type of misconduct, and not there to be the agent, owner, or object of the stain.

I cross-posted this to SuttaCentral -- Questioning the translation of AN 8.15, “Misconduct is a woman’s stain”.
I also wrote there that I think that the translations (or at least the interpretations) of most of the other stains are questionable too.