Good translation, Grace.

> og spurði hver þær mundi hafa til gefið
> and asked who of them (male and female) have given (it)

Magnus Magnusson and Hermann Pálsson note that "In all probability a
silk cloak was a highly decorative and expensive garment that could be
worn by a man or a woman." But Flosi specifically uses the female
pronoun, 'hver þær' "who (which woman) among them...?" Presumably he's
already made up his mind that it's an insult and wants to resond in kind.

> Skarphéðinn mælti: "Slíkt er illa mælt að sneiða honum afgömlum
> Skarphedinn spoke, "Such is badly spoken to taunt him ???

'afgamall' "very old". 'afgömlum' is dative (because the verb 'sneiða'
takes a dative object), in apposition to 'honum'. It could be
translated fairly literally as "such is ill-spoken, to mock him, an
old man", or, more idiomatically, "It's bad to speak like that, to
mock an old man like him", or as Magnus Magnusson and Hermann Pálsson
have it: "It is wrong to mock him in his old age."

> því að margir vita eigi er hann sjá hvort hann er heldur kona eða
karlmaður."
> because many know not when (they?) see him which he is rather woman
or old man."

"because many don't know, where he is seen (MM & HP: "just by looking
at him"), whether he's a woman or a man (a woman rather than a man)."

As well as meaning "to see", 'sjá' can be used impersonally, as it is
here, to mean "be seen". Zoega: "(5) impers., þá (acc.) mátti eigi s.,
they could not be seen; sér þá hauga enn, those mounds can be seen
yet; má þat ok s., at nær standa vinir Gunnars, it may be seen, too,
that Gunnar's friends stand near him; [...]"

'karlmaður' "man" (as opposed to woman). This word is a referrence to
Njáll's sex rather than his age.