I think the title says it all. Basically, when a new comment appears on your targeted post, it sends you a PM about it.

@PostWatchBot@lemy.lol

Usage

• Subscribe to a post: just mention the bot in the comments or send the link to the bot via PM.
• Unsubscribe from a post: send PM to the bot with stop text and link of the post like stop https://lemmy.ml/post/1234
• Unsubscribe completely: Send PM to the bot and add stop text to your message. It will unsubscribe you from all subscriptions.

Note: the bot sends only one notification per post. It waits for the previous notification to be marked as read for new comments.

Made with @CannotSleep420@hexbear.net's lemmy-bot project 🙏 Tomorrow I will publish the code publicly after adding README and self-hosting guide.