I fly for an outfit where either pilot can call the abort. We also operate a policy where the NHP (PM) can call 'what he sees' leaving the PF to make the call, even if the PM is the captain and the PF the co. As PF we will always have a hand on the throttles until V1 is called.
Not sure I can ever see a scenario where an abort was called below V1 when the captain would know better and ignore it. If you abort below V1 then you will always be safe and at least can talk about it safely and comfortably in the crewroom.