By news@appleinsider.com (Malcolm Owen) Twitter will allow users to “undo” mistakenly-posted tweets in its app as part of its upcoming “Twitter Blue” subscription, a researcher has uncovered, with the $2.99-per-month service also potentially including other useful premium features.Twitter is a free service to practically all of its users, with advertisers providing the bulk of revenue. However, the microblogging site may soon give users extra features in exchange for a relatively small monthly fee.Uncovered by …

Source:: Apple Insider