Keyboard selection is inconsistent, and I believe it's a bug - it's definitely not a behavior I would expect or have seen in any well-respected editor that comes with custom key bindings. The problem is that Cmd+Shift+Right/Left selects the text by expanding the selection to the end/start of the line without ever deselecting the text if the cursor goes over existing selection. The above behavior is opposite of selection by word via Option+Shift+Right/Left which has the right behavior. This behavior exists in all apps that don't come with custom selection behavior. For example, Google Chrome, TextEdit, Slack, etc. I spent a long time with Apple Support to fix this because this behavior doesn't work for me in XCode and it can be frustrating at times because I often have to use mouse which I don't like. Can anyone help me improve this please?