In my mind, Jepthah very probably did sacrifice his daughter. Does this prove that what he did was accepted practice by Jews for centuries?? No. Was Jepthah grieved by this oath? Yes.
Does the Bible state that God was pleased with this? No. God's reaction is not recorded; in fact, the book of Judges is filled with what people did when people just did "what was right in their own eyes." It's kind of the theme of the book, if you read it in any direction.
It is hard to say why God allowed the daughter to come forward. It seems they recorded this because of the realization that they would be responsible for making rash oaths. [Didn't cure them of it, though. There were a group of Jews who bound themselves with an oath not to eat or drink until Paul was dead... and God delivered Paul, so these guys either had to starve to death (keeping the oath) or else break that oath. I personally think that God would not have held them to that oath if they had repented of their murderous ideas first.]
None of the "proofs" that have been presented on the thread so far has impressed me. Do you have anything more substantial, or is this it??? (Seriously!)
bebu
edited to add: I'm not disputing that human sacrifice ever existed/was practiced. It apparently did in Canaan, and it was, I recall, one of the reasons God judged the people there so fiercely. I also don't dispute that the Israelites began to follow pagan practices, including human (child) sacrifice, during the time of the divided kingdom... This lead to the exile, another judgement from God. But what impartial evidence has shown that the nation embraced this practice as part of the Jewish religion? That God endorsed it?