I don't want to vigorously defend the organization of the git repo, but browsing the source code of Smalltalks is always an issue. The source code is closely tied to the "browser" and for the longest time this was the only way to view the classes contained in an image. At some point mechanisms were designed to serialize the code to source control repos. The relationship of Smalltalk and version control systems is a difficult one.

In the case of Newspeak, I only would edit the raw source code if I had no other way to do it. It is so much easier and ergonomic to use the Newspeak IDE to view and modify the code, with the live debugger, object introspection and all the advantages that the IDE gives you. The recent addition of exemplars, where working fragments of the code are part of the documentation, is especially nice.