Concerning the second dummy, referred to in your initial post, Walke agrees that there were two of them, a few weeks apart. He mentions them both in "Scenes and Reminiscences," p. 350. But I have never found where anyone came up with the "Deluded People Cave In" slogan that was supposedly painted on the second one.
The wooden dummy episode WAS one of the great hoaxes of the War, but the hoax was not on the Confederates. It was on the latter day American public who believed the story about the boat being sent down to rescue "Indianola."
Concerning Porter, it has always amazed me how revered he was. Even after the War, no one ever spoke out about any of his obvious character flaws. He was either very powerful or very charismatic. His biographers seem to hold him in awe. The most amazing thing I've ever seen in this light was his ability to get a gunboat deck log changed to make an account of a routine battery-running on Red River match up with his grossly exaggerated tale of an epic Naval adventure of one tinclad against 18 Confederate cannon. (In fact, there were four cannon present at the event.) Of course, there's also his getting a cannon captured by the Army at Fort DeRussy in 1864 moved to the Washington Navy Yard, where it is inscribed as being captured by Porter at Fort DeRussy in 1863. The man had no shame.