You are making a very good point. Right now it can't give such indication because it is a black-box model. There are hundreds of inputs that go in (eg. characte

You are making a very good point. Right now it can't give such indication because it is a black-box model. There are hundreds of inputs that go in (eg. characteristics of the code, how much the author has worked with this code in the past, how frequently this part of the code changes) and the output is how confident the model is that the contribution is safe to merge. With that said, there are ways of exposing more details to developers. For example, scoring is done per-file, and Codeball can tell you which files it was not confident in.