This discussion reminds me of two things.
1: In our first house, a new build, I put a curtain rail up in the bedroom. Called the wife upstairs to see if she was happy with it. "It's on the piss! Did you not use a spirit level". Of course I did, hence confused. Obviously the window wasn't level. It looked fine with the curtains close

. Lesson learned there about doing it right or doing it so it looks right...
2: When we had the old brick porch ripped out at our current place we had an open porch constructed instead, with an oak post at one end. All the white paint that had been put on the inside of the old porch was stripped off what was the original and again now outside wall to strip it back to brick. I was oiling the post one day when an old chap walking past stopped to tell me the post wasn't vertical. I disagreed, sure that our builder had managed to get a fairly chunky oak post right. Still, had to check with a level to confirm. However, the original '30s brick front wall of the house around the door, and therefore in the background of the post as you looked at it, is definitely on the piss, hence why the old bloke thought the post was off.
