Clearly, it depends on the abilities of the reader what kind of code he/she can understand. Compare it with, say, Chinese: If I gave you a child book written in Chinese, and you didn’t speak Chinese, you won’t be able to understand it, even if every kid (or grandmother) in China can.

On the other hand, if I found out that someone working for me was spending hours in trying to make his code understandable by his grandmother, I’d probably fire him for wasting my money just to keep his grandmother busy.

I’m not saying that clean code isn’t important. But if code is communication (which it is), and every communication is interaction (which it is, too), then, as with any interaction, the outcome depends on all participants. You can’t replace a well-rehearsed team with “clean coding style”.

For example, if you are going to take notes in a class so you can study it later, you can use whatever structure you want for your text.

But if you are publishing your text on a blog for example, you have to write better than that! People can’t understand your hacky notes made quickly while hearing the class.

Normally this notes are disposed after a few days, but if you kept them for a year and tried to read, you will most likelly have a really hard time. But code normally is used for a relativelly long time, so you may want to keep it as understandable as possible. If possible, on a extreme case, your grandmother will be able to understand parts of it: “get_comment”, “update_comment”, “change_theme”.