Is static from synthetic mousepads a problem for mice?

No, it’s rarely a problem. Modern optical and laser mice have robust internal shielding, so surface-level static won’t interfere with tracking or electronics unless you generate a visible spark into the USB port. The real risk is only with cheap, ungrounded mice in low-humidity rooms, and even then it’s just a momentary cursor jump. For 99% of setups, this isn’t worth worrying about.