Will Libra be able to replace Bitcoin? I believe it won't. So, I don't think we should ask the question in OP, because both Facebook and its coins, Libra are worse than bitcointalk.org, and Bitcoin, respectively. Facebook platform also does not have good systems to control their quality of their community posts. Actually, they have reports but such things are not enough for huge platform like Facebook. Reporters should have rewards from their good reports.