"Why would Jesus preach to those devils who are kept in chains under darkness reserved for the future judgment?"

To rub it in. "And having spoiled principalities and powers, he made a show of them openly, triumphing over them in it." (Col 2:15)

You must have missed that the passage which speaks of him preaching to the spirits in prison (the very passage you are arguing about) talks about him preaching to the spirits who were disobedient during the days in which Noah was building the ark (which certainly is not talking about Abraham and Moses)?

1 Pet 3:18-22 (KJV) "For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: {19} By which also he went and preached unto the spirits in prison; {20} Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water. {21} The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ: {22} Who is gone into heaven, and is on the right hand of God; angels and authorities and powers being made subject unto him."

You will note that when referring to human beings, Noah and his family, he says "eight souls" but when speaking of those in prison to whom Jesus preached he says "spririts." Why? Dictringuishing human from non-human?

Yes, those in Abraham's bosom are included later on, but are not said to be in "prison," as we find in 1 Pet 4:6 "For for this cause was the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit." This one is spoken of the saved dead. But where does it refer to them as being in prison? It does not.

As far as my calling Calvin a heretic, BTW, I was referring to this specific statement "If Jesus had died a physical death merely, it had been nothing. It was necessary also that he suffer in hell." That is heresy. It is a denial of the cross. It says essentially that Jesus dying on the cross was just a necessary prereq to going to hell so he could burn and that salvation is actually accomplished by him frying not by dying on the cross. This contradicts the whole of the Bible, which does not say one word about Christ burning in hell, but only about him dying on the cross and going to hades (not hell) and being raised the third day.

Its an accurate portrayal of what a logical person would take from the parable as rendered in the KJV. He asked for one drop of water? "Must not have been too bad then." KJVOism makes a mockery of hell, turning hell's waiting room into hell itself, making hell into a walk in the park compared to what the Bible actually teaches it is.