  Bazlov generalized the construction of Fomin-Kirillov algebras to arbitrary
finite Coxeter groups. They are quadratic approximations of Nichols algebras
associated with the conjugacy class of reflections and a (rack) 2-cocycle q^+
with values in {-1,1}. We prove that q^+ is twist-equivalent to the constant
cocycle q^-=-1, generalising a result of Vendramin. As a consequence, the
Nichols algebras associated with the two different cocycles have the same
Hilbert series and one is quadratic if and only if the other is quadratic. We
further apply a recent result of Heckenberger, Meir and Vendramin to classify
the finite-dimensional Nichols algebras of Yetter-Drinfeld modules over the
dihedral group or order 2n, where n=r or n=2r with r odd and not a power of 3.
