Excoriating Diana for whoring suggests that making the deal she did with Milohai was, in isolation from prior commitments, somehow un-virtuous
Which it is, by amazon standards. I repeat:
She takes an expression of love that was supposed to be exclusive and reciprocal and freely given and a deep lifelong commitment, and hands it to the first stranger who was willing to pay.
That doesn't sound like a completely bog-standard condemnation of commercialized sex to you? "Expression of love" and "reciprocal and freely given" are as important there as "exclusive" and "commitment." And anyway you can't actually separate cultural antipathy for commercial sex from cultural antipathy for casual (ie non-relationship) sex, it's the exact same taboo. See also: the utter interchangeability of the insults "slut" and "whore" despite technical differences in meaning.