Great list. I'd add 1) Don't build things into libraries that are convenient for you but inconvenient for others. 2) Never muck with low level code except in dire need.

Do you enjoy finding the weak points in things? Do you use new devices, maps, etc without reading the instructions because you just think you should just know how they should work? Do you find that alarm bells go off in your head when you read a phrase that could possibly interpreted in more than one way? Do you often use things in ways that they were never intended yet those ways seem the most logical to you? Do you possess powers of intuition that lead you unforseen vulnerabilities? Do you find the needle in the haystack? Coding isn't inherently more interesting than testing. Anyway, if you identify with any of these phrases, you can apply it to testing...

I took no computer science classes in college although I did take math up to Calculus. I taught myself some stuff about computers, read a few books, played with programming on my own and took a few community college classes and now work as a programmer. I've worked with people who got phds, they have the same job. Funny, sort of. I mostly goofed off and had fun in college and got a degree after 5 years... in Ecology.