There has been a fair amount of debate about the question of when, where, and how Abinadi returned to the City of Nephi. It appears humorous that he would come to the city in disguise, but almost immediately identify himself as Abinadi. However, I think he came in disguise for a limited purpose. Because there was an arrest warrant still outstanding against him (Mosiah 11:29), he needed a way to covertly enter the city. But once he was in the right place within the city center, he was ready to identify himself and deliver his message.
Book of Mormon Central, "Why Did Abinadi Use a Disguise? (Mosiah 12:1)," KnoWhy 310 (May 8, 2017).
Alan Goff, "Abinadi’s Disguise and the Fate of King Noah," Insights: A Window on the Ancient World 20, no. 12 (2000): 2.