I accept all 1:1 trade offers from the same set, as long as your trade offer is at least neutral^^

Explanation:

• Trade is good if my progress towards set completion advances. A A (before) <-> A B (after)

• Trade is neutral if my progress towards set completion stays in-tact. A B (before) <-> A C (after)

• Trade is bad if my progress towards set completion declines. A C (before) <-> A A (after)