Twitter is exploring adding a feature that would let users flag tweets that contain misleading, false or harmful information, according to two people familiar with the company's projects. The feature, which is still in a prototype phase and may never be released, is part of the company’s uphill battle against rampant abuse on its platform. It could look like a tiny tab appearing in a drop-down menu alongside tweets, according to the people, who spoke on the condition of anonymity because they were not authorized to release details of the effort. Twitter has been plagued by many issues, such as fake accounts that can be purchased outright for pennies and that spread automated messages and false stories. Extremists use the service as a recruiting tool, and hate-spewing trolls have threatened…