I wouldn't go as far as to say it can't harm paint. But then again DOT 3/4 fluid is pretty much 100% guaranteed to damage paint, so its much safer. It also has a higher boiling point than regular old DOT 3/4.
Silicone fluid is actually hydrophobic. It will not absorb water. But that doesn't mean water can't get into your system, only that if it does it will stay separated from the silicone fluid. This is actually worse than being absorbed, since pockets of water can form and cause corrosion.
This is a big problem if you're upgrading to silicone fluid. You have to flush your brake system very well, any remaining old DOT 3/4 will cause pockets of contamination that can cause corrosion (ie, a pocket of DOT 3/water sitting in your caliper). And since the rubber parts in the braking system absorb the old fluid over time, its best to use silicone fluid in a new system (one that has never seen DOT3/4). Also, not all old rubber parts are compatible with the silicone fluid. Typically all the new rubber parts are, but its not 100%.
Also, while it doesn't eat paint, it can contaminate your work space. If you're painting a car, it will cause "fish eyes" in the paint if present. And it only takes a tiny amount to contaminate an entire work area, so keep it away from anywhere you might shoot paint.
Finally, a last fun fact. If it somehow gets pulled past a leaky vacuum booster and into the intake system, it turns into silica when burned. Silica=sand. So, don't let it get burned in your engine. DOT 3/4 doesn't do this.
