Personally, I think that Steve Moore is going way too far in placing any alleged "Guede-as-police-informant" theory front and centre.
While I think that it certainly cannot be ruled out as a possibility, and while it certainly fits with certain key evidence regarding how Guede was treated in the days and weeks prior to the murder, there's currently no positive evidence that Guede was a Perugia police informant.
And what's much more important is the simple fact that the "Guede-as-police-informant" theory is totally unnecessary to a cogent, coherent explanation of how/why Knox and Sollecito were wrongly charged and found guilty of the murder of Meredith Kercher. In addition, there's no evidence that the police/authorities made any effort to "protect" Guede after the murder, and there's also no evidence that they even suspected Guede of involvement at the time when they arrested Knox and Sollecito.
As many of us have outlined here and elsewhere before, there's a depressingly simple explanation to what happened to Knox and Sollecito in November 2007 and thereafter: a rush to judgement, tunnel vision, confirmation bias, groupthink, deference to senior authority figures, a group "circling of the wagons", and personal/collective hubris. None of this need have anything whatsoever to do with whether or not Guede was a police informant.