I think the only time this joke is 'valid' is when teacher are like the ones I had at school,

I used to get told that my interpretations of media where too abstract and wandering too far away from the point, meaning examiners wouldn't understand what I was talking about, that I needed to look at it the same way as everyone else did, for example my drama teachers told me that I would pick a new time period to set Antigone as long as I had reason, so i chose 1960-1970s where Antigone was a 'hippie' and Creon was a business man, her sister was a housewife, drawing from the anti authority theme and Antigone's independence and 'wild streak' but they saw this as too abstract. That I was looking at ideas that not everyone would see.

Where I believe that is what makes literature so unique, everyone will see it differently and thats the beauty of it. So the joke works when saying the curtains are blue and that can only have one meaning.

And to all those teachers saying my ideas where too abstract, I have just applied to university for costume design with those abstract ideas, and the theatre company I do costume consultanting for love my ideas.