The Paradox of Abetment: A Section 107 Conundrum

I'm totally stumped by S. 107 of the IPC. The doctrine of abetment seems to be turning into a puzzle in my head. If a person instigates or encourages another to commit a crime, it's considered abetment, right? But here's where it gets tricky - if the abettor is also a participant in the crime, then isn't it just considered as a co-accused? I mean, think about it - if someone is both encouraging and actively involved in a robbery, how can we separate their role from that of the main accused? And what about the distinction between aiding and abetting? Is it just me, or does this section seem to be sending mixed signals?