It would be nice if there was a visual indication of which body text was going to be used as preview text for the questions page and chat oneboxing (if they used the same amount of text, then only one indicator would be necessary, of course).
There are two advantages of this:
- This text is the third most important content (after the tags and title) in terms of convincing users to view the question (and then answer it, vote for it, share links to it, etc). Like the first sentence in a news article, it should be the most enticing. It would be useful to know exactly which part of what you're writing will be shown.
- When the spoiler tag is used, it should come later in the question, so that the hidden text isn't visible in the previews. It's difficult to know exactly how much leading text is required at the moment.
The indicator could be something subtle like a (subtle) colour highlight of the text, or some sort of symbol marking the end of the preview sections, or it could be a separate "what will this look like on the questions page" preview.