Well, to my knowledge, track limits have varying degrees. Basically you need to keep 2 wheels within the white lines, but if you run wide in an area where you can't gain a lap time advantage, then the lap is legal. However if you cut a corner to gain a faster time by putting all four wheels outside of the track limits, then the lap is illegal.
This seems to be the case in F1. They're constantly reviewing the track limits on a corner-by-corner basis per track. I think I remember Martin Brundle saying that it was hard to know where it was legal to run wide on certain corners, especially at Abu Dhabi.
In the case of Blackwood, I was more concerned with the chicane before the long straight because it clearly had advantages if you cut it. I try to make it obvious where you shouldn't cut a corner, but nothing is perfect. I replied to this post because I thought that MicroSpecV had a slight complaint about a turn which I thought was very lenient.