Twitter Inc is building a new feature that will allow users post messages as long as 10,000 characters, Re/code reported on Tuesday. Twitter has been experimenting under Jack Dorsey – the company’s co-founder who returned as chief executive in October – to make the website more engaging. In the few months under Dorsey, Twitter introduced the ‘Moments’ feature, added polls to tweets, rolled out a “buy” button and replaced its star-shaped “favorite” icon with a heart-shaped icon called “like”.