The tweet is not advocating print debugging per se, but about understanding the code by modifying it. This is how I approach any foreign/old code all the time, I can recommend it. If you have a theory about how it works, edit it, and see if your edit works expected. It may or may not, either way you learn something. I love debuggers, but editing the code can also help you trigger a breakpoint just before that special case hits. Much faster than conditional breakpoints.