Should you ever tap the "report" button, the app's terms confirm that Facebook is well within its rights to retain any data you upload for as long as they deem necessary, with no statute of limitations. A similar data-retention scenario emerges every single time you block or mute someone within VR. If a stranger approaches you and does something unwelcome, and you choose to proactively push back with built-in block or mute functions, Facebook may silently and invisibly sic a moderator upon the situation to see what happened and how you may have reacted or what you might have said or done in response.
Even worse, if someone "near" you in an official Facebook VR space blocks or reports a user, even if you're just minding your own business, your behavior (including motions and speech) may be tracked by these same silent, invisible Facebook moderators. That data can be stored on Facebook's servers indefinitely without you being notified.