Business Insider's Lara O'Reilly takes a pulse check of roundtable attendees.Victoria Baud for BIAI is shaping brand reputations in new ways — and that requires new approaches from brand leaders.Business Insider gathered a group of executives to discuss "The New Rules of Reputation" at Cannes Lions.They shared specific tips for navigating this evolving landscape.It's no secret that many unofficial channels — like Reddit threads or customers post…