In this quick Nuke tip I explain why I don't think anyone should use the mask input on the merge node and why I think building a script that is easy to read is an important part of compositing.
Check out the Zen of Python here: https://www.python.org/dev/peps/pep-0020/
And the Python Style Guide here: https://www.python.org/dev/peps/pep-0008/