When you leave a comment at a Christian's blog there is a good chance it'll say "your comment will be visible after approval." It will not say "if your comment doesn't express overt agreement with the post or offer some sort of praise for the blogger, there is a slim chance your comment will see the light of day," but that's sometimes what they mean. Some bloggers let their comments post immediately but if the comment isn't particularly flattering or asks a pointed question, it stands a good chance of being deleted once the blogger (or his minions, if he's high on the food chain) sees it.
Within Christian culture they tend to only publish the comments that praise the blogger's godly character or say what a blessing he/she is to others. Pastors of mega- or multi-campus churches are a prime example. If their blog even allows commenting, try leaving them a neutral or inquisitive comment and see if it makes it past customs.
Here is a pop quiz. Which of the following is an actual, published blog comment and which is a comment that has been denied publication at a pastor's-or-random-Christian's blog? Pick A or B:
A. "You have been an inspiration to thousands and a blessing unto this world."If you guessed the published comments were A's and the denied comments were B's, you get an A+.
B. "I am curious as to why you don't make your salary public and why you drive such an expensive car."
A."You are our gift from God. Thank you for answering His call."
B."I've tried to set up a meeting with you but they keep telling me you don't meet with people personally."
A."I want to thank you for imparting your wisdom to myself as well as others. Your godliness is an inspiration."
B."You said you are accountable to a team of people, and I am curious who that team is accountable to."
A."In the eyes of God, few people upon this earth have ever spread the gospel with such conviction and sincerity."
B."I'm wondering if you're going to address the congregation about the domestic violence report that came from your household."
Many Christian congregations aren't encouraged to approach the pastor if something he says or does seems sketchy or unbiblical. Within American Christian culture it's common for the pastor to be seen as infallible or an untouchable celebrity rather than a friend and companion in seeking God. This mentality comes in handy for deflecting any concerns about the pastor's actions or teaching. Surrounded only by positive feedback the pastoral staff's ego metastasizes and Jesus diminishes. You can certainly do this, but don't call it Christianity.