I don’t mind some repetition. This has been going on for a few years now. But one example of reduced culpability, or maybe not culpability, would be those who believe that marriage is dissoluble at the cause of adultery, and marriage again is not a sin. This is a common teaching among other Christians. Additionally, it is a common teaching that even when divorce is a sin, one can still be forgiven and then be re-married. It is not an ongoing sin. A person may be a a spiritually strong Christian, and still ignorant of the Catholic theology of marriage. Then when the second marriage is with a Catholic, or they try to convert, they are not morally culpable of mortal sin, but cannot receive communion. This is one rare situation, but it does happen.