In the embedding example here the initial topic post doesn’t show up. Is it possible to have the first post show in embedded comments?
No, this isn’t possible. The assumption is that the first post in the topic will be identical to the blog post that you have added the embed code to. For this reason, the first post is not included in the embedded comments.
Is there some way to change this behavior? We’re embedding discourse for questions on a chapter and we attach several discourse topics to a page.
There isn’t a setting that can be used to change the behaviour. It is possible that it could be achieved with a plugin. The only other option I can think of would be to use the Discourse API to pull the topics and responses to your website.