Here is a link to my original reply post which you are talking about:
Websleuths Crime Sleuthing Community - View Single Post - Amanda Knox tried for the murder of Meredith Kercher in Italy *NEW TRIAL*#10
The negative of her leaving was that it might make her seem more suspicious, in two ways:
1) draw unwanted attention to her. Unwanted attention might lead to closer examination of her. For example, let's say police had some more questions for Amanda, such as going over again what was her last interaction with Meredith, or something like that. They discover that Amanda is back in the U.S.. Then they have to figure out how to ask her these questions while she is in U.S., etc., this draws extra attention to her. In the meantime, someone says, "hey by the way what is her alibi for that night?" Closer examination, etc., etc.. Last thing she would have wanted.
2) raise suspicions of her if police were having any questions about her. Example: investigators find some Amanda DNA in the bathroom. If Amanda is there, they can ask her and she will say 'well, yes, that was from when I took a shower that morning, remember? I went to the cottage to take a shower.' Or some other DNA of Amanda, she can say, well I was there at the cottage, I did this or that thing, that is what that must be from. Now, let's say she had already gone back to the U.S.. Investigators find some of her DNA somewhere. Go to ask Amanda some more questions, discover she has gone back to the U.S.. Again, this draws extra attention to her. Now we have this curious Amanda DNA at the murder scene, and yet she has left and is not available for questioning. Perhaps this fact will lead to closer independent examination of her alibi and what she was doing night of murder, etc..
So really, Amanda's thinking was not very far-off. Her act of leaving could have really added extra attention, raised suspicions, etc..
The problem, is, though, that there were innocent people who did not need to be worried about the repercussions of their act of leaving, and so they did leave. And so this places Amanda in the position of being compared with girls in a seemingly similar position, who acted much differently to her in regards to this issue of leaving or not leaving.
However, as I said, these girls were in reality not in the same position as her. Because they did not need to worry about the repercussions of their actions and how it might be interpreted by those close to the investigation.
I guess we do not really know if Amanda made the right decision or not. Because if she had left, and any of the above which I laid out had happened, we would be saying, Oh she should have just stayed in Perugia and not drawn attention to herself.
But since she stayed, we do not know what would have actually happened in the alternative. And so we can say, 'she probably should have just left when the other girls did.'
I guess she was really stuck in the situation of, it could have gone both ways. And she chose to stay, how much difference that made in the big scheme of things, I don't know.