Unfortunately I learned this from experience. Cilantro may put mercury into circulation and even expel a bit of mercury out through the urine but it isn't a chelator in the true sense of the word. Chelate in Greek means claw. The "claw" (chelator) attaches itself to the metal and takes it out of the body.
One of my friends is on disability because she used cilantro tincture and the effect nearly killed her. Using a bit sprinkled on your food is a condiment is unlikely to hurt anyone.
By the way I'm a certified nutritional consultant and have read countless books on fasting and experienced it myself. When the body suddenly releases toxins like mercury and the organs are not prepared to handle such a big load then the mercury can be trapped in the thyroid. A basic knowledge of the endocrine system which I'm assuming you have or else you wouldn't have commented should tell you what that means.