Used to work on a P.O.S. [as in retail] system in the mid 90s using a custom IBM BASIC compiler.
A parade of consultants had touched the system's source code, but I'd often see:
'DO NOT DELETE THE FOLLOWING LINE OR IT WILL CRASH
followed by some string operation before calling a procedure.
Well, that dev hadn't read the manual - which clearly stated that the WHOLE STRING, not a reference, was passed on the stack when calling a procedure....