Any chance of modifying the font size on your blog? It's enormous, I literally had to wheel the chair back to read it. And I'm quite old!

Naaaaaaaaaaaaaa! You're so old-school!
Why don't you try and learn a real, effective and modern branching pattern? Like this, for example
http://nvie.com/posts/a-suc...

1. For weeks at a time, an individual branch can be in an undeployable state

Not true. You're free to merge the trunk with any developer's branch (not the opposite, as Martin Fowler says!).
Hence, you can do Continuous Integration and check the deployable state of anything you wish

2. the development team will report that merging is a major part of their day, and fraught with complexity given (1)

Merge is a nightmare only if you continue suggesting the use of SVN

3. Often there are regressions, as a merges are missed, and the business yells at the IT dept.

Merges missing? Obviously, SVN can't store a merge (it is not even displayed in the graph). Again: old school, my friend. SVN is a fossil.

4. Labeling and handling labels makes you consider another career
This is your problem. For me, labelling with SVN is a nightmare. With git, mercurial and Bazaar labelling is easy as breathing.

Of course, my previous comment has nothing to do with the topic of your article, Abstract branching, which is really cool and amazing

Branch By Abstraction as described does not involve branching. So it seems you aren't communicating an idea very well by labeling is as something that it isn't. It should be "Feature Toggle Instead of Branching".

Would you prefer I rename the article to "Branch by abstraction instead o branch by source control" ?

"Branch by abstraction"--misleading name I agree--is different from feature toggle/dark launching.

The aim of feature toggling is to test and release incrementally. Branch by abstraction abstracts code as a stepping stone in a larger refactoring effort. Check out http://continuousdelivery.c...

and if you use SVN you can find my little utility helpful for automating merges (contradicts good developer instincts, just as it contradicts mine :) but I find it highly useful).

https://github.com/livepers...

I don't like the cascade model - https://paulhammant.com/2013...
I appreciate you're tool is clever, but I'm never going to recommend cascade in the enterprise.