My comments are deleted. Anyone know why?

I heard that to post on Reddit, you first need to build up your karma by commenting, so I’ve been commenting on “Casual Conversation,” a subreddit recommended in the tips section. However, it seems that most of my comments are being deleted by the moderators. I haven’t made any negative comments or posted URLs, and I haven’t been spamming the thread either. I’ve been posting about one comment every two or three hours. Honestly, I have no idea why they’re being deleted. Do you know why?