Here's an easy test: Any time the pronoun "you" is used, then something in that sentence is potentially personal toward the person being written to.
That is true. Someone told me that I wasn't a Christian the other day on a thread. Seeing how much Christ centered stuff I do and am involved with, it made me unhappy, but I realized he was replying to the writer of the post I had posted.
I erased three different replies to him, basically quoted some scripture that made me feel better, and said, if he had a complaint, to take it up with the original writer of the post instead of me, and that I wasn't going to continue in an argument.
But it does make me see red first when people tell me I don't love the Lord. A person might not agree with my church or my theology, but to doubt the level of my commitment is one of the things that really irks me.
It gets tricky for me to keep my conscience clean at moments like that and turn the other cheek, but I am working on it.