After upgrading from OS X Yosemite to OS X El Capitan Developer Preview, I tried to edit /System/Library/LaunchDaemons/ssh.plist to change the default SSH port to a custom one. This is the process I've been using for a couple of years in previous Mac OS X versions
The problem is that El Capitan doesn't allow me to change anything in this folder (not even with "sudo"). The folder and its files are marked as "restricted" when I list the contents with "ls -lO". The same folder listing in previous versions of OS X does not show "restricted". I've recently to learned that this is due to SIP (System Integrity Protection) - https://forums.developer.apple.com/thread/4002 / https://forums.developer.apple.com/thread/4662.
Question is, now with SIP, what's the "politically correct" way of changing the SSH port?