Most of this is good stuff I agree with, but depending on "$0" to be a usable path to the executing script isn't the most reliable technique, and when it fails it will be pretty confusing.
I tend to use a big multiline string for my usage information, instead.
Thanks for the comment!
I like to say perfect is the enemy of good. $0 is not perfect but good enough in most situations. I think it's a good trade-off compared to the 15 lines better solution :)
Knowing it's not perfect is important though, I won't mention it in the post because I believe comments are an actual part of the article itself, so your comment on this point is good!
You're right on multiline strings, they're probably better everyday. I wanted to show off weird stuff with this example. In practice though I have noticed people are more prone to update the #/ comments than a usage string, I have no idea why.