if the original code writers had used comments and asserts to not only assert their assumptions but then maintain those assumptions over time, then you wouldn't

if the original code writers had used comments and asserts to not only assert their assumptions but then maintain those assumptions over time, then you wouldn't have to. plus, they'll probably introduce less bugs and debug faster in the future. i can only speak from my own experience, thought processes and developing skillset. everyone's different. some people can keep track of numerous complex relationships in their head for months on end.