Who are the sinners in the vestibule of hell?

I assume from the terminology that this relates to the Comedia of Dante Alighieri.

The sinners in the Vestibule (Described in Canto III) are the Futile those "whose lives knew neither praise nor infamy" (ibid l. 36) and including "that caitiff angel-crew/Who against God rebelled not, nor to Him/Were faithful, but to self alone were true" (ibid ll. 37-9).

These figures represent those without conviction either to good or bad. They are represented following a banner that wildly flaps around in the same way that their opinions and values shifted in life.

The only identified figure is "The coward spirit of the man/Who made the great refusal;" (ibid ll. 60-1) it is uncertain who this represents although it has been suggested that it is Pope Celestine V who abdicated the papacy in favour of Boniface VIII who Dante hated; it has also been suggested as an identifier for Pilate who condemned Christ despite believing His innocence.