I think the reason it sounds so creepy is because of a combination of things: hair coming is such an incredibly intimate act, we're aware of IT's other threads and we can presume there is a control/sexual element involved in the desire, and the T is naive enough to be entertaining the idea of allowing IT to actually perform the act (IF we accept that IT is being genuine).

In general, I think the act of combing a T's hair is a huge boundary violation because it is far too intimate for a healthy T/client relationship. However, I think there are other instances in which the desire might come from a more infantile place and, therefore, be less creepy. For instance, it it were a young female client with maternal transference or a female client with DID and "inside kids" then it would read differently. It would be about craving nurturing or wanting to bond with a maternal figure as opposed to a desire to exercise control over a woman or engage in an intimate act that might serve as a substitute for sex. That's why, coming from an adult man who has made sexually suggestive comments (is the baby mine?) and who has expressed a desire to control T's appearance, it reads as "acting out" in a very inappropriate way. Rather than indulging IT, it seems the T should be asking probing questions about control, power, male/female relationships, etc. in order to help IT learn these kinds of things so that he has the potential to have healthy relationship IRL. If the T indulges him and says "yes, comb my hair the way you like it," and then IT thinks "women should allow me to choose their hairstyle," that is teaching IT the wrong thing. IRL, men do not have the right to choose their gf/wife's hairstyles. IT should learn that he does not have that right, and understand WHY.