For the most part, people on Hacker News want to read thoughtful and insightful comments. They want to learn new things, or gain new perspective, or otherwise extract value from the comments they read.

Comments about religious history (especially with sources) or religious artifacts (like manuscripts), clear explanations of interesting doctrines, and descriptions of how different religions/sects view some particular issue tend to be pretty well received. As a religious person, I've made a lot of comments along these lines (some about my own religion, some about other religions) and gotten a lot more upvotes than downvotes for them. Even the negative responses I get are thoughtful most of the time.

Assertions that religion X is true/false, statements that aren't backed up by appropriate evidence, and preachy comments tend to be poorly received.