If there are things in the Activity Feed that you don't want showing up, you can delete them from the database.

The feed pulls from the action table. For instance, if you want to delete all entries that involved pushing up a branch called offending with commits, then deleting that branch, in Sqlite:

snippet.sql

SELECT * FROM action WHERE content LIKE '%offending%';
DELETE FROM action WHERE content LIKE '%offending%';
SELECT * FROM action WHERE ref_name LIKE '%offending%';
DELETE FROM action WHERE ref_name LIKE '%offending%';