Thanks for the query, Moin!
This mod provides a starting category picker, and lists individual topics moved out of that category by date:
-- TOPICS MOVED LIST
-- [params]
-- date :start_date
-- date :end_date
-- category_id :cat_id
SELECT
pr.user_id, pr.post_id, pr.updated_at,
(regexp_match(pr.modifications, 'category_id:\s*-\s*([0-9]+)\s*-\s*([0-9]+)'))[1]::int AS old_category_id,
(regexp_match(pr.modifications, 'category_id:\s*-\s*([0-9]+)\s*-\s*([0-9]+)'))[2]::int AS new_category_id
FROM post_revisions pr
WHERE (regexp_match(pr.modifications, 'category_id:\s*-\s*([0-9]+)\s*-\s*([0-9]+)'))[1]::int = :cat_id::int
AND pr.updated_at::date BETWEEN :start_date::date AND :end_date::date
ORDER BY pr.updated_at DESC
