Learn Swedish: Hårfästet och rynkorna, dem vill ingen prata om. - The hairline and the wrinkles, nobody wants to talk about them.

This is a resumptive pronoun used in a structure called left-dislocation. We announce the topic first (Hårfästet och rynkorna) entirely outside the main sentence structure, and then immediately refer back to it with dem. This puts a heavy, conversational emphasis on the topic before the actual sentence begins.

Why is the pronoun in the object form dem instead of the subject form de?

Because it acts as the object of the preposition om at the very end of the sentence (nobody wants to talk about them). Even though the pronoun is pulled to the front of the clause, it keeps the object case required by its logical role in the sentence.

Since Hårfästet is a singular neuter word, why do we use the plural pronoun dem?

The pronoun refers back to the entire fronted phrase: both Hårfästet (the hairline) and rynkorna (the wrinkles). Because there are multiple items connected by och, they form a plural group and require the plural pronoun dem.

Why does the verb vill come before the subject ingen?