The antecedent of they is “the crowd” of verse 15, and Good News Translation has made this identification for its readers.

The text does not say where the crowd gathered, but it is most likely at Pilate’s house, which translators may need to make explicit in the text.

Christ is translated “the Messiah” by Good News Translation in order to show that the word is to be understood as a Messianic title rather than as a proper name (see 1.17). “The so-called Messiah” of New American Bible and An American Translation is perhaps even closer to the full meaning in the context, since Pilate’s question was no doubt sarcastic. In place of Jesus who is called Christ (so also verse 22), Mark has “the King of the Jews” (15.9).

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .