Personally I found the biggest improvement to my own software came from maintaining the same system that I wrote for 4+ years.
If I came back to a part and didn't understand it more or less immediately, then it was time to refactor it. I wrote the code I should understand what it is doing. No excuses that someone else had written bad code.
"It was hard to write, it should be hard to understand." (I was joking, of course, when I said this.)
It seems to me that that's a reasonable metric for determining if something was well written or possibly well commented. I had an opportunity to go back to some of my older code about a year ago. It was scary to me what portion of it I no longer understood. Worse yet, portions of it referred to documentation that I could no longer find. The company had migrated their documentation through several storage organization technologies and no one seemed to know where the old stuff went. Luckily I ran across a retired engineer who recalled where a lot of it had been archived.
(Unrelated) When I read the article, the first thing I thought was that all of the simple programs had already been written.
Personally I found the biggest improvement to my own software came from maintaining the same system that I wrote for 4+ years.
If I came back to a part and didn't understand it more or less immediately, then it was time to refactor it. I wrote the code I should understand what it is doing. No excuses that someone else had written bad code.