Actually the nucleus disruption seems to be still the best option.
1. As my calculations yesterday pointed if there would be anything active in coma it would correspond to one spherical nucleus with diameter 630 - 100 meters. If there will be more subfragments (as seen in C/1999 S4 (LINEAR) case) such active surface can be easily reach by larger number of 20-50 meter sized fragments.
2. Comet brighten nearly as simple reflecting body, actualy if some post-disruption larger subfragments keep to disintegrating, amount of dust in coma will grow and brightnes can slightly grows.
3. Ion tail is still not present, there is small or no outgassing in coma.
4. Spine tail a synchronic feature observed in case of disintegrated comets is present, and even it looks that brightness is enhanced towards this tail, which indicate that majority of dust comming from this event.