I think it is best to split this into 3 sub section.
- Discussions with the Sutta is tagged
- Discussions where the Sutta reference or title appear in the subject
- Discussion where they appear in the body
Each division being progressively more noisy than the other otherwise as more discussions happen this becomes more and more noise than anything useful.
Also sorting can be added by: resend activity score (you need time decay of activity); hence a mix of freshness and activity.