The second point I think is particularly interesting. It means:
Ruser who does not consider themselves an expert programmer could be maintaining code that they understand, but could not be expected to create from scratch.
Let’s have some sympathy for the part-time
This is the point we will emphasize in our new example.
Read on for a particular example. I think this is good advice to generalize: write your code to make it as easy as possible for “part-time” users. This applies to custom code you write as well, as unless you are constantly in a particular part of the code base, you’ll forget the details later and have the same problems that a part-timer would have working with a different language.