Good points, marred by what appears at first blush like double standards. Why are you willing to selectively discount some DNA evidence while you admit other ?

You say "the supposed Sollecito DNA on Meredith's bra clasp just plain does not count" - what is that "supposed" doing in here ? The FOA site admits that the clasp was shown to carry small amounts of Sollecito's DNA.

Why does it "not count" ? Admittedly, the handling of that evidence may not have been up to the standards normally demanded by the judicial system, but why should that matter to a Bayesian analysis ? All we're interested in as Bayesians is the ratio between P(DNA on clasp|Sollecito guilty) and P(DNA on clasp|Sollecito not guilty).

The defense may well have its own convenient narratives about how Sollecito's DNA "could have been transferred to the fastener in any number of ways" owing to carelessness on the part of the police. Those narratives are just as much noise as all the other noise you've pointed to. The details of US Department of Justice guidelines for forensics are also burdensome details for the defense.

The danger of coming across as arrogant - that is, more confident than your own entanglement with the evidence justifies, not the jurors' or someone else's - is that it provides others with an excuse to abandon the hard work of thinking rationally about the case, and letting themselves be swayed by the affective components: pretty pictures of Meredith or Amanda.

What I liked about your previous post was that, without any rah-rah propaganda about rationality, you outlined a procedure for laying out our current state of (un)certainty while minimizing some of the predictable biases. There was something delightful about the implausibly level-headed discussion thread it generated. We started with an open, almost playful invitation to rationality, in a spirit of inquiry.

Here we seem to be back to a spirit of established truth and advocacy, a spirit of "getting at the teacher's answer" - we even get averaging of the students' grades. I'm expecting the discussion to be more run-of-the mill, too. (Your Postscript is also mildly insulting; if someone is smart enough to arrive at the appropriate level of uncertainty in Knox's guilt, then surely they are smart enough to figure out what to do about it.)

Here, I believe, is the bottom line. Make rationality fun, and people will play along without for a second realizing it's hard work. Make rationality sound like something people ought to have, to be as smart and righteous as you - that's a turn-off.