I am continuing with my recondite but edifying series on epistemic modality. This instalment's a juicy goosey.
'Could be' assertions have a different kind of role, depending on whether one takes one's audience to know more or less, and also depending on levels of mutual trust.
'Give me your personal details' - 'No! You could be an axe murderer!'
'Could bes' in internal accounting, vs. conversation.