With all due respects to +Chrysostomos, there are several things that are being overlooked. First, Christ states very plainly that He is the "door of the sheep" and all who enters "will be saved" (John 10:7-9) What Chrysostomos is proposing is that we can enter the door and leave. But our Lord stated, "I am the door; if anyone enters through Me, he will be saved, and will go in and out and find pasture." (John 10:9) One cannot leave.
Secondly, our Lord states, "I am the good shepherd and I know My own and My own know Me, even as the Father knows Me" (John 10:14) Our Lord plainly states that He knows who are His own. How could one turn from Him that Christ already knows? Christ states that "I must bring them and they will hear my voice" (John 10:16)
Finally, please note there are those who are NOT Christ's sheep (v 26) and there are those are (v 27). We're given to Christ by the Father (v 10:29). This, by the way, is a recurring theme throughout John (v 6:39, 6:44, etc.)
Chrysostomos mistakenly takes the vineyard example and applies it "to every soul". This is not what our Lord is saying and many people stray into error by presuming something not there. In the vineyard example, our Lord Jesus is speaking about the covenant being taken away from the Jews.
I'm not sure what Luther's interpretation is but I can certainly read the text.
Well, duh. That is the whole argument, that there is no once-saved-always-saved security among sheep.