Many horse players seem to ignore it.
It's an important factor, and weighing in light is breaking the rules.
So is weighing in heavy.
As far as UK/Irish racing rules go, I think I can top this DQ.
Every race has a listed starting time over there.
For example, if the 2:15 at Ascot goes off at 2:14, it can be declared void.
It's happened there before - can't remember the track, or exactly when.
Starter's watch was a bit fast - oops!