The minor third is a staple interval in nearly all musics of the world, and is one of the central intervals in western music.
In 31-ET, the minor third is much more in-tune than in the standard 12-ET. Compared to 12-ET, the minor third is significantly wider, much closer to the natural interval. This makes the minor third sound more consonant, more stable, and warmer in 31-ET than in 12-ET.
As it matches the 6:5 ratio in the harmonic series, the minor third implies a root that is a perfect fifth below the top note, or a major third below the bottom note (implying a minor chord). However, the minor third's tonal center is weaker than that of perfect fifths and fourths, and in a minor chord, this root is overridden, and the fifth determines the root.