Function without_member 

pub fn without_member(
    state: Vec<RawStrippedState>,
    user_id: &UserId,
) -> impl Iterator<Item = RawStrippedState>

Drop the entries occupying a user’s membership cell.

The invite route appends its own copy of that event, whose sender the origin check bound to the sending server, so a copy the sending server chose is never the one to serve.