Very well said. Thank you for the time you put into it.
And most especially, thank you for saying something that needs to be said over and over again until everyone in the universe understands it: Programmers should not expect to be able to open a source file at random, move to some arbitrary point within that file and then instantly be able to modify the code there from just a cursory glance at the code and comments in the locality.
I cannot tell you how many times I've heard "This program worked fine until the last time we had it modified by our usual programmer, and ever since it works fine most of the time but every now and then doesn't work at all". It's always always always because their "usual programmer" modified the thing without bothering to gain sufficient understanding of the program as a whole entity.
When I hear that story from a potential new client, I won't even look at the code until I'm on the clock. Too often, that other guy in whom they've lost confidence has been given one last chance and is out there feverishly kludging together yet another bandaid pseudofix. His desperation will always move faster than my diligence.