These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Hilarious in Hindsight: One of the RAF squadrons has the callsign Batman. This sounds a lot funnier/weirder now to audiences who are unaware of what a batman was in the military.
Fair for Its Day: The film makes a point of showing that initial German bombing of London was an accident and the retaliatory British bombing of Berlin was not.
Special Effects Failure: Early in the film, German fighters are strafing an airfield, when two fighters strafe the same Hurricane on the ground, the strafing pyrotechnics on the ground go off in the wrong order. Also, one shot of a German bomber exploding in mid-air is clearly the explosion effect composited over the still-intact Real Life airplane.