https://www.youtube.com/watch?v=Wk26fX0XI0s&feature=youtu.be

In the above link, the player in question seems to be killing lots of players he isn't actually hitting according to what the spectator sees.

He was marked as clean https://bf4db.com/player/1697802244

My question - if this is clean, then how can a user such as myself determine whether this is a spectator glitch or the person is actually using software to register non hits as hits? 

Consistency helps. If they’re consistently doing it across multiple rounds/servers then it’s less likely a spectator glitch. It’s not 100% but it’s something.