but it's funny watching you try to decipher the words of others who can. I will give you one point for realizing there is no human test for sincerity, but I believe hannahmontana was referring to sincerity from God's point of view. In which case, a conversion is sincere if God is the cause of it (Ephesians 2:8-9).
BTW, the unforgivable sin is attributing to Satan the works of the Holy Spirit. Jesus said,
"Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven. Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come." Matthew 12:31-32
The preceding verses put this in context where we see the Pharisees accusing Jesus of performing miracles by the power of Satan.
Ron Paul - Honorary Founding Father