I am not attacking you, or even saying that I didn't have a similar response when I first read the above passage, but I would like to submit a few things.
1. The scenario in question is comparable to an arthritic submissive man or woman who enjoys rope play. His or her dominant partner has an obligation to both see that the submissive's welfare is accounted for, and fantasies addressed. I imagine that a responsible partner would not dabble in rope play immediately following knee replacement surgery or even a day particularly rough on the joints, but to ignore that need entirely would be yet another defeat in the ongoing struggle arthritis presents. This does no service at all to the submissive partner, except in highlighting his or her weakness.
2. There is nothing more empowering than facing down a perceived weakness. We can agree that eating disorders are mental illnesses, but a great many people suffering from various mental disorders consider them mental weaknesses. An agreement that despite prior problems, this is an issue that needs to (or would simply be exciting to) be faced, coupled with affirmation from the dominant partner that it's not just an exciting thought, but something he or she truly believes the submissive capable of doing- that's downright euphoric.
3. What we do is dangerous. Even the least edgy kink can seem uncomfortably far from safe, in some capacity. By definition, alternative lifestyles/preferences are not conventional, and you can easily find twenty people singing a chorus about how damaging x, y and/or z kinks are to you. But the real truth is that the human condition is dangerous. Is it different if, in a vanilla relationship, a partner comments thoughtlessly on his wife's weight, triggering her into a bulemic state she'll never tell him about? Yes. Can you imagine being in an in-depth submissive relationship without disclosing that information? Or, if you can, is it possible that anyone would find it acceptable and healthy for that disorder to remain hidden from your partner once it reared its head again? The original situation was not a Dom blundering blindly into a minefield, it was a calculated risk. And I have to tell you, that's what therapists get paid $200/hour to do, with less information about their patients, usually.
Nothing works for everyone. We all have different limits. Awareness is important, for both partners. Communication is equally important.