If you are not the CEO or a top executive, investors won't care, or even know. It's best to diversify. Even if you lose out on potential future appreciation - and get market returns instead - it's a dramatic reduction in risk, and presuming you get a lot more value out of the first few million than in more millions later, it's usually a good tradeoff.
If you are the CEO or a major shareholder, consider establishing a planned schedule of stock sales. Investors will not be so concerned about a gradual selloff that appears to function more as a method of providing constant cash flow.
if your an insider and you need to worry about signaling or legality. again probably need a financial planner.