Though this has been discussed a number of times, allow me to take one more run at it.
As the OP of the question in question, I feel that it's important to leave code samples in a question intact because in many cases, the code in question is what's causing the problem.
In this case in particular, I had the syntax wrong and that is what prompted the question in the first place. If the syntax had been correct, the W3C validator would have been happy and I would have not even thought that self-closing tags wouldn't be valid.
In a more general sense, people primarily ask questions when something happens that they didn't expect and they don't know why. If that something involves code that doesn't behave as expected in some way, it's crucial to leave that code as-is because changing it (particularly to be "correct") negates the entire point of the question.
In this particular instance, the self-closing syntax being incorrect everywhere in the question is illustrative of the OP (me) not realizing that it's incorrect and makes it more clear (or at least likely) that the issue isn't just a single typo, but is a deeper or more systemic issue.
In this case, "correcting" any of the syntax errors is 100% inappropriate because the entire question is about the (unknown) syntax errors. Altering this only makes things less clear.