hi, incest survivor here.
maybe im misunderstanding but i thought when lizzie said "There are no consequences for the incest there, whether between cousins or siblings or uncle/niece, aunt/nephew or even parents/children (Craster)." since the second part of the statement was "The reason we don't practice incest in the real world is because it has consequences for the children born of it, whether mental or physical. That's not the case in the ASoIaF universe, where a beating also has mental and physical consequences." that it explicitly referred to mental & physical health states, as in physical & mental disabilities & not as a reference point for the emotional impact that incest can have.
i haven't seen any correlation to defects similar to the habsburgs despite it constantly being brought up by people who are very anti house targaryen or those who shame aegon ii's child jaehaerys for having six fingers, which seems less related to the incest & more of something that seemed to have happened (& this isn't including the amount of people who think targaryens genuinely birth dragon-like children prematurely as if most of those instances didn't contain outside blood magic interference.) however, there are cases in asoiaf of characters reacting negatively to their incestuous status but i think, culturally for valyrians, it doesn't nearly have the same impact on them as it would other families were they to adopt a similar pattern.
this isn't in defense of incest or anything — but moreover a suspension of belief for myself in particular as i find a lot of incestuous media uncomfortable, but simultaneously intriguing. the targaryens, like all valyrians before the fall, practice incest to keep the magic to fly dragons within their bloodline. this is all george expects us to think about it, so for me, as someone who survived assault all throughout my childhood, it's easy to pocket in "these are fantasy elves" compared to crastor who physically disgusted me, because his goal for reproduction was to sell his newborn sons to the wights to prevent them from overrunning his home. to me, his daughter-wives responding negatively to it was much different from alysanne & jaehaerys (& more couples i'm too lazy to get into) who rushed to be secretly married because they loved each other.
& this could be primarily a kink for george as incestuous relationships are also heavily featured within another project he worked on, elden ring. these families are dysfunctional, of course, but miquella the kind is a much more nefarious character compared to some of the targaryens who married direct siblings (with aerion and aerys & aegon iv being similar to miquella, although naerys was noted to be in love with her brother aemon instead). because we only have one pov targaryen character in daenerys so far, we see that she was resigned to the fact she might marry viserys one day.
i don't think lizzie is a reportable freak for saying "The problem in the series is not incest rather the abuse and treatment of women from men whatever from their family members or not" because.......it's true lol. of course there are instances of problematic incest within the series, but it also is heavily impacted by the period's violent misogyny.
this doesn't mean within fanfiction the negative impacts of incest aren't interesting to be explored, as one of my favorite fics from this fandom at the moment explores the potential of daemon's complex feelings towards viserys stems from childhood abuse — but within the text, it isn't significantly supported, no.