WHy so angry? Your experience is your own, and it is nice that you shared it, but your experience is not the norm. Disney is under no obligation to accomodate any dietary issue, and when i comes to buffets, there has been almost no reports that they will allow a child price for an adult. In ten years your report is the first I have read, so I understand that posters wanted to warn the OP that she may not be given the same grace you were. Perhaps restaurants outside of WDW may allow you the reduced price, but in WDW most buffets and AYCTE meals are also some sort of show or involve characters, and so you are paying for that. Even if you wnated nothing ore than a chair, you will be charged full price.
No one is disputing the restaurants that allow adults to order off of the childrens menu. TS restaurants do not have to allow that either, but most will.
ETA- my DDIL has had this surgery well over 10 years ago and the amount of food she actually consumes would not keep a bird alive. In the entire time I have known her, she has never asked for any special accommodations, and has never insisted restaurants are obligated to address her appetite as a medical issue. If we go to a buffet she will choose items she wants to try, eats what she can, and then my DS or DH generally will finish what she took, and that's it. If we go to dinner anywhere, she either will share with my DS or me, and we pay the plate fee or will order her meal and then bring the leftover food home. The idea that any business is responsible for anyone's appetite is ludicrous, and the fact that Disney should be forced to do so in order to avoid a confrontation with a guest is truly frightening to me. Disney already makes so many accommodations to ensure that guests who need them can safely eat, but as we see several times a week, there are those who take advantage in order to avoid eating food they either do not like or to make substitutions that seem to be tastier. WE have seen so many Disney courtesies discontinued due to this kind of practice, and as a Nana who was grateful to have a safe place for my DGD to eat for an expended period of time, I am offended whenever anyone practices this kind of behavior.