'If it's in the book it's a defect'
Not if you're a captain with a leading Brussels based airline! Numerous times I've seen defects such as flap faults, airbrake uncontrollable, etc in the tech log, prefixed with 'FOR INFO'. The crew then fly the aircraft back the following day. Illegal and dangerous, not sure I'd be happy with my kids flying on that leading Brussels based airline if that's their attitude to safety.
As far as misunderstandings go, I always use a continental style '7' with a line through it, seen 7s confused with 1s quite a lot; cue a defuel when that happens!