Startups typically depend on serial infusions of funding from backers to get through their early years, and a so-called down round—raising money at a lower implied valuation than before—is a big black eye. So lately, companies have gotten increasingly creative at trying to avoid being considered less valuable, particularly when investors seek to unload their stakes, either out of disenchantment or because they need the cash for something else.This has sparked a sort of tug of war between investo...