Kevin, I don't understand its significance.
Please can you go into more detail about how this changes anyone's thinking on the subject?
This is a great question, and I guess some further explication is in order.
The significance is that it refuted two well propagated apologetic talking point about the Kinderhook Plates and Joseph Smith's Egyptian Alphabet & Grammar project.
Most people focus on the first point, which is that it proves Joseph Smith did in fact produce a translation of at least one character. Now why is this significant? Because it is beyond dispute that the plates were a hoax. So it proves Joseph Smith can produce "revealed translations" from a bogus source. Which is precisely what the critics have been saying all along, while the apologists have been using the "revealed text" in Mormon scriptures as evidence that he is a prophet, suggesting these story lines couldn't have come about any other way!
As to the second point, Bradley's argument comes while the Book of Abraham/KEP/EAG debate had reached a climax and just began to subside. The timing was perfect. Apologists had started to argue that the evidence found in Joseph Smith's Egyptian Grammar didn't constitute translations ("deciphering") at all. Will Schryver had just argued in a much ballyhooed event, that the EAG project was just an attempt to encipher and already translated text. But Bradley shows that Joseph Smith, in an attempt to translate the Kinderhook plates, consulted the EAG in order to derive some meaning from the first KEP character that resembled a character found in the EAG. Now why the hell would he want to do that if, as the apologists had maintained, 1. Joseph Smith knew the Kinderhook plates were a hoax and 2. the EAG was just an abandoned project that involved nothing more than a failed attempt to "encipher" an already translated scripture? This was a double-face-palm for the apologetic community, and I can only wonder how many in the audience realized it at the time.
Incidentally, from my conversations with Don prior to his presentation, my sense was that he didn't fully grasp the significance of his finding. He was just so excited about the correlation between the two documents that no one else had ever noticed before. FAIR didn't grasp the significance either, or else they probably wouldn't have allowed him to present it.
Oh, and it should go without saying that the tiny minority who disagree with Don Bradley's discovery, is led by none other than William Schryver, who, thanks to Don, saw his relevance and credibility go from celestial to telestial within the fifteen minute time-frame it took him to present his findings.