It's pretty random who gets banned for botting from what I've seen.
Prime example: 2 friends botted 99 WC at about the same time. Used same scripts, and botted around the same amount of hours straight at a time.
One got rolled back to 75 from 95. The other got 99 and never had any issues.
I can't really say what jagex's bot detection system looks for, because I've personally never seen anything so random before.
My main account (level 135) has 11 99's. Of those 11, 9 are botted. I've never had any problems.