Some open-source, client-only software which would let me easily save, search, and review all the gibblegabble I write on places like HN or Reddit etc. It would

Some open-source, client-only software which would let me easily save, search, and review all the gibblegabble I write on places like HN or Reddit etc. It would need to capture more than just my posts, since replies need context and that context might also contain the necessary search-terms.