Definition: Given the Question and Answer pair, detect whether the answer is acceptable or not. Denote acceptable answer as "yes", otherwise denote as "no". An acceptable answer is consistent with the context in question, detailed, long, and uses general knowledge of English. Answers that are not definite and suggest a variety of options are not acceptable answers.
Input: Question: I recently had somebody tell me that a mutual friend of ours who is genderqueer prefers that people refer to him/her using the gender-indefinite pronoun they. In some cases, this almost seems okay: Kris left their umbrella at our house. On the other hand, if Kris is sitting right next to you, it feels very odd to say They (meaning just Kris) would like more cake. Or even odder, Kris would like some more cake, can you please pass it to they/them?" Are these usages grammatically correct? Are they in the process of becoming grammatically correct? Are there more correct alternatives? 
Answer: My main gripe is the gratuitous change of number that sometimes happens when someone is trying to avoid gender-specific pronouns. Example: [old way] "Everybody has at least three dollars in his wallet." Formerly, when the gender of the antecedent was not specified the pronoun was forced to masculine. [misguided attempt at gender neutrality] "Everybody has at least three dollars in their wallet." Everybody is singular in number, which is why we do not say, "Everybody are going to the movies." [how I would do it] "Everybody has at least three dollars in its wallet." Gender is forced to neuter using an already-existing pronoun, and singular number is preserved. The following may prove useful to the OP.

no