Thank you - Thank you also for the feedback. Part of writing the article was also to fill in my blanks.
I didn't know that sub-flows duplicate the code but that duplication is machine generated duplication, i.e. it's all in the server so the frontend user isn't aware of it. I would compare this with hash-defines in C whereby the compiler will expand them all out and the compile the resulting code. For the programmer this isn't a concern since it all happens in the compiler. I would take sub-flows, from what you describe, to be the same concept.
I explicitly left link-calls out since that would be getting to technical IMO. Good to know there are multiple approaches to avoiding code duplication.
The deep linking can be useful if you have complex flow and there is something amiss with a single node. I use it for highlight points in my mind maps, for example, https://demo.openmindmap.org/omm/#flow/a6381cd32644cdf0/n/c6e2de8178aac0b1
Id after the /n/ is the node id. If click on the link, it will show the flow and highlight the node in question. So it has nothing to do with execution of the flow and is purely a frontend feature for sharing specifics with other people. Since it contains the node-id, these links are not intended to be long lived since nodes can disappear, so this would be something for a slack chat or messaging someone.
I hope that clarifies what I meant by deep linking in this case, the term deep linking comes from a previous life of my and means something completely different in the world outside NR - I understand the confusion 
