I have found the saying of al-`Abbaas' feet dragging on the ground. This is not in any Shee`ah book, it is in a book by a Zaydi scholar Abu al-Faraj al-Isfahani's (d. 356) Maqaatil al-Taalibeen, pg. 56, (chapter on al-`Abbaas b. `Alee b. Abee Taalib). Abu al-Faraj uses purely Sunni chains in this book.
Well, in the section where he mentions the feet dragging, there is no chain, except that he mentions a companion of al-Baaqir and al-Saadiq . His name is al-Kumayt b. Zayd. He has said this after narrating a poem about him.
وكان العباس رجلا وسيما جميلا يركب الفرس المطهم ورجلاه تخطان في الأرض وكان يقال له . قمر بني هاشم . وكان لواء الحسين بن علي " ع " معه يوم قتل
"And al-`Abbas was a handsome and beautiful man, he would mount the beautiful horse and his feet would exceed (dragging) on the earth. And he was called: 'Qamr Bani Haashim. And he was the flag bearer of al-Hussayn b. `Alee with him on the Day of the Murder"
Abu al-Faraj al-Isfahani, Maqaatil al-Taalibeen, pg. 56
It is impossible to say that al-Kumayt b. Zayd al-Asadi knew how al-`Abbaas b. `Alee b. Abee Taalib looked like. According to Mu`jam al-Shu`araa', al-Kumayt b. Zayd was born in the year 60 and died in the year 126. So he lived from 60-126. Also, al-Dhahabi has said that he has died between the years 121-130 in hisTaareekh al-Islaam. al-Khoei says in his Mu`jam Rijaal al-Hadeeth, that he died during the life of Imaam al-Saadiq .
So how is al-Kumayt saying how al-`Abbaas looks, when he was only a 1 year old when Karbala' happened. Also, there is a gap between Abu al-Faraj al-Isfahani (d. 356) and al-Kumayt b. Ziyaad (b. 60 - d. 126).