[glenjamin]

If a tree falls in a forest with no-one around, does it make a sound?

While the list of techniques here look like excellent ways to uncover unknown unknowns, be sure that it's actually valuable for you to resolve these issues.

In almost all cases the goal isn't to create perfect software, it's to create effective software - and sometimes the ROI on these unusual cases doesn't stack up (or doesn't stack up _yet_).