In Derek's example the switch and the bulb are 1 meter away from each other and therefore the time is 1/c seconds, i.e the time light takes to travel 1 meter.
The topic is definitely a little confusion, but there are no GR violations.
Perhaps I didn't make my example clear. Imagine loop with 2 switches...one switch 1 LY away...another switch 1 meter away.
Derek flips the 1m switch and light instantly turns on: What does that tell you? Derek flips the 1m switch and light doesn't turn on: What does that tell you?
How were you able to find out that information before waiting 1 yr?
https://news.ycombinator.com/item?id=29283101
From what I understand, in your setup the lightbulb will turn on and quickly turn off, irrespective of the state of the other switch which is 1 yr away. Then after 1 yr passes it will react according to the state of the other switch.