I think parent is addressing the situation where the company is giving the employee the stock for free, trying to avoid there being an out-of-pocket cost for the employee. In that case, the value paid is 0 and the entire value of the stock is taxable income to the employee. An 83(b) doesn't solve the problem here because it just makes the IRS calculate the spread on the day of the purchase, rather than at the time of each vesting event, but there is still a taxable spread on the day of purchase.
