I have just noticed, that if you have an .plist file in your Xcode project (it does not matter whether it is the Info.plist file or other - in my case it was other .plist file) and you edit the file as a source code file (right-click on file Open As->Source Code File) and then you switch back to XML property List (right-click on file Open As->XML Property List), make some changes and save, then all your formatting and comments are dropped when you open it again as a source code.
Does anyone know how to deal with such behaviour? Do I have to stick editing the file as source code ALWAYS?