You bring up good points and my article would need some clarification on some parts, I agree on that. I'll just write quick replies back to you, and try to format something on the article itself later.
Purge really did free memory and quite a lot. I'm not too expert (as you probably can tell) how the OS X memory management works, but I mostly settled with solutions that seemed to help my problem. Maybe there was some third party software that messed things up.
The problem with the inactive memory is that it is not freed, it is swapped. So when hitting memory limits of my system, the computer started swapping. Just freeing the memory, in my case, would have been much quicker. Practically my machine was constantly swapping when the memory limit came up. As you said, repair disk permissions caused all this to happen due to filling memory with disk cache. So that was a nice solution to my problem; a way to force swapping on inactive memory.
Python point is bit wrong, I was indeed trying to argue that installing python packages is impossible through homebrew. However, I did use a lot pip+virtualenv, so that's at best a bit vague argument on the OS X side. However, in production I always rely on the packages provided by the OS, not pip + venv, unless really necessary. This is mostly because it makes it easier to keep system up-to-date.
I'm sorry if this showed up as uninformed rant, but I just wanted to share how I felt using OS X and Macbook for a year as my primary computer.