Just wanted to chime in here! I think the implementation of cross-posts is up for interpretation (and can definitely be changed if one is preferred over the other). Generally speaking, there are two types of implementations:

Cross-posts only copy over the title and link of the original post

• This is what Thunder currently does, unless it's a text-only post (in which case, it copies over the text content of the original post since that's the only relevant part of the post)
• The idea here is that we typically want to change the contents of the cross-post to be relevant to the community that we post to.

Cross-posts copy all content of the original post (title, link, body)

• This is what Lemmy UI does, but it injects "crossposted from" into the body of the post
• This can be useful if you want to post the same post across multiple-communities with the same body

From this discussion, I do think that it could be valuable to add an easier way to inject the original body of a post into a cross-post. If you would like this to be a feature, please create a new feature request on GitHub!

A side note on cross-posts:

I believe that Lemmy considers any posts with the same link as a cross-post. There's no distinction (from the API) on which post was the "original" post, or whether a post was crossposted "from a community" vs "to a community". This is also the reason why there is additional metadata for each "cross-post" in Thunder. The additional metadata allows you to figure out when a given post was created to find the "original" post.

If you're curious about specific implementation detail, @micahmo@programming.dev might be able to answer them!