The original designer may have been over his head, but he added comments. Engineers need to be rewarded for code quality, as in proper comments, coding guidelines, naming conventions, etc. To many engineers write code that is impossible to understand or modify. Any code that is worth writing is worth modifying, and that means thinking of your successor while you are writing it.
Most of us have probably had at least a few experiences in dealing with SED (Someone Else's Design), and indeed it can be frustrating. As in Dwight's case, my own experiences usually involved a request to add features and/or increase performance of an existing design -- "re-use with changes" -- after the original designers were long gone from the company.
In most cases, re-use with changes didn't save any time compared to just doing a new design from scratch to meet the new requirements.
I would much prefer to have the problem of what to do with OPM (Other People's Money) :)
This is a great story that explains what a real engineer needs to do - not just design, but troubleshooting to find a solution when something doesn't work as it should - in this case when a spec. was changed.