In the last month, a pair of food delivery startups were battling complaints about their tipping policies. Customers and workers chastised the companies for unfairly using tips to subsidize worker pay. As the furor grew, one of the companies, Instacart Inc., changed its compensation policies to match some of workers’ demands. Meanwhile, the other company, DoorDash Inc., stood firm. It still uses tips from customers to offset some of the minimum payment that a worker gets for each delivery job, in which “Dashers” travel to restaurants or stores and bring food to customers. That decision apparently hasn’t harmed DoorDash’s reputation in the eyes of investors.