Any conversation with a deceased loved one would be probably be a one-way conversation but who is to say that this loved one could not hear you. Yes, the person had died, and maybe was in the grave for years but God is not constrained by man's concept of time. You die, dead for a 100 years yet for the deceased there is no consciousness of the elapsed time. Dead one second, with the Lord the next second.
God always was, is, and always will be. Yes, even though the person is dead that you are talking to and in the grave, in God's construct of time that person is actually in heaven at the moment that you are talking to them. There is certainly nothing wrong with saying good-bye to a loved one. I did this when my late second wife died a premature death. It brought comfort to me even though I realized that I was probably just talking to myself.
Personally, I really don't give squat what some church forbids but rather only what God forbids. Jesus talked to Lazarus who was dead for 4 days and told him to wake up. The thing about the 4 days, I read somewhere that this is the official length of time before a person could be declared dead by either Jewish law or tradition and that was the only reason that Jesus tarried a bit when He heard that his friend was near death. He didn't want anyone of Jewish origin to claim that the guy wasn't dead before Jesus made him rise out of the grave because he was not dead the official 4 day period. Interesting.