If this is the case, though, and Bob knows it, why on earth would he specifically thank Harry for ordering him to lose the memories forever ? [ DB end of chapter 3 ]
How about because (when he's the Bob we all know and love) he hates being like that, so he was glad that Harry wouldn't be asking him to keep flipping back and forth in order to plumb that side of him for knowledge?
In your model, it makes no difference for how Bob interacts with potential future holders that Harry does so. In mine, that's the point at which he cuts off evil necroBob, and we don't have to come up with some explanation for how at a later point he managed to do so without specific instructions despite having no free will.
I'm not sure that that's completely true. To me, it seems like an order, once given to Bob, is permanent, with the exception that future orders can counter previous ones. So if he was so ordered, then it would take an order from a future master to overrule it, potentially giving Bob a much longer period of time before the memories arise again.
Exactly.
The difference between Free Will and just Will seem somewhat ambiguous, though. We know that Bob does have Will, just not Free Will. So with the understanding that whomever holds the skull controls Bob, once the skull is put down, who's to say that Bob cannot use Will to pick between two equally valid owners? Cowl did hold him last, but Harry was closer and actively seeking to reconnect their bond.
Which would be where I note that Grevane actually worked the Darkhallow, and all Cowl does is stand at the focal point at the very end. Though I think it is entirely possible that Bob could plausibly fake enough Darkhallow lore to keep Cowl satisfied off the top of his head.
How could he fake any of it? If he cut off all of his relevant memories, then he wouldn't have anything with which to fake. More to the point, why would he even want to fake it, given that that would be disobeying his master, the one who was holding his skull?
Either following Harry around through DB or having been in Bianca's place in GP while Bob was warning people off Harry's stuff work for me.
What was your theory for why he didn't just take Bob right then?