If - and it’s a huge, astronomic IF - Harris is able to control Trump and shut him down using his own methods, biting back on merit of personal authority when he attempts to interrupt her, then hot mics would benefit her enormously. I don’t think it’s easy to do, as Trump has proven time and again that he can bulldoze people on sheer respectlessness, loudness and tenacity. Given the risk of him running her over being a disaster for her momentum, I think it’s probably safer on balance to have muted mics.