The "chatgpt" community on Lemmy.world has 217 posts. To rank the top 15 posts with the most engagement, I'll need to fetch and analyze the data for these posts.

Unfortunately, specific engagement metrics (like upvotes, comments, etc.) for individual posts are not accessible through my current tools. However, you can check the posts manually on the community page to identify the top ones based on the upvote and comment counts shown next to each post.

If you need more specific details or have another way you'd like to analyze this community, let me know!