A reader, BlogsDNA tipped me off on a new Google test. It appears that Google is showing a form of sub links under the main search results, that link to additional forum threads, when relevant, from a specific site. Here is a picture showing two such cases for a search:

I personally do not see this in any browser I tried, nor on any platform. But it does seem interesting. Often discussion forums have many threads about the same exact topic. This gives Google a way to include multiple threads without cluttering up the search results with indented results from the same site.

I am not sure if this will stick, but it does look interesting.

Forum discussion at Search Engine Roundtable Forums.