@BernardSheppard @danluu I don't think point 1 can reasonably be inferred. The fact that someone programmed in instructions for dealing with a particular error doesn't mean they thought the error was likely. I've been in that position myself - I'm writing some small portion of a program, I see that it doesn't handle a particular error condition, so I put in a brief explanation of what needs to be done in case that error ever happens, even if it seems like the error is supposed to be logically impossible (e.g. if another part of the program is supposed to prevent it).

Or perhaps the instructions are generic, meant for handling a whole class of unlikely but serious errors, and in that case we can infer nothing about how likely the particular error that caused this situation was thought to be.