I didn't really understand what the point of the post was. Maybe because it was so cautiously phrased. I mean, the post said that she had no problem with erotic fantasies, but then it gave the impression as if the only "responsible" way to write certain topics was the "take them serious as RL issues and do research" approach, it seemed?

I'm not into incest fic, so I'm unsure about fictional tropes there, but the same kind of argument exists with research for rapefic. Which, sure, is a good idea if anyone wants to write fanfic about rape as trauma realistically, but not so much if the point is to write a rape fantasy played out by characters. I mean, for example, I like rapefic of the kind where essentially the rape is fetishized, as porn, but the other kind of rapefic where the rape functions mainly as trauma and is dealt more or less realistically doesn't work as porn for me even if the descriptions are explicit. If it is heavy on the hurt it can work for me for my character hurt/torture kink, but that isn't really a "porn kink" but a "plot kink" for me. Along the same lines most porn slavefic wouldn't really be improved by researching human trafficking and its psychological impact on the victims, and I really don't see why anyone should do research into that to write write their "they get kidnapped, enslaved and humiliated by the bad guys" epic, or risk to be accused to make lightof human slavery.