Like the 4chan posting option, consider adding some feature to BLF where you can click a sagecheckbox in the >Additional Options... menu which automatically, when replied, moves the topic down the forum page by three or more spaces. If the forum fetches posts from say, a MySQL database, then using the ?topic=XYZABC.FOO string for fetching the post on index.php, you can simply manipulate the database entry. Because the forum automatically lists forum posts at the top in bumping order, you could perhaps use the new sagefeature to artificially reduce the last maybe 10 bumps.
Also consider adding a sageing limit so you could only sage ONCE a topic to avoid a single user abusing the sagefeature, and if anyone abuses it through spamming on multiple threads, just ban them or something.
