WASHINGTON, Aug 27 (Reuters) - The U.S. Securities and Exchange Commission (SEC) on Friday issued a request for public input on so-called digital customer-engagement practices by brokers and advisers amid growing investor worries of such innovations that involve predictive analytics, differential marketing and behavioral prompts designed to optimize customer engagement used by financial firms. The SEC consultation, which Reuters first reported on Tuesday, will help the agency consider whether these practices should be governed by existing rules or may need new ones, agency chair Gary Gensler said. read more