Re: bbpress.org plugins page
“Read More” is handled by a filter on post_text.
The different topic sorting is accomplished by creating custom functions with the right SQL queries.
The RSS feeds display topics instead of posts. This involves the bb_rss.php_pre_db hook, the $bb_db_override global, and some voodoo.
All of this is part of a set of fairly involved plugins (and more) that listen to changes in the SVN repository where the plugins are stored.
As an aside, that site will soon open up to anyone wanting to host the plugins they write.