en_tn/mrk/15/18.md

began to salute him

The reader should understsnd that they were mocking Jesus by pretending to salute him.

Hail, King of the Jews

The greeting "Hail" with a raised hand was only used to greet the Roman emperor. The soldiers did not believe that Jesus was the king of the Jews. Rather they said this to mock him. (See: rc://en/ta/man/jit/figs-irony)