Thank you very much for your comprehensive reply. I hope not only me but others get more clarity on this issue.
My concern is that voting Socialist in Australia, at least at present, does not result in a seat in parliament. In the meantime, the Greens is what we have and they do have a sizeable presence. I'd like to vote for Socialist politicians (not that there's any where I live) if their preferences go to the Greens because we must keep left-wing reps in parliament.
One thing I don't want to see is the disunity that plagues leftist movements in other places. Otherwise, we all lose, including the working poor [edit: and all others living hand to mouth] and the environment. Compromise is inevitable. What is important is that we don't compromise what is essential like real care for people and their struggle.