  We prove that the existence of $\mathfrak{c}$ incomparable selective
ultrafilters implies the existence of a Wallace semigroup whose cube is
countably compact. In addition, assuming the existence of $2^{\mathfrak c}$
incomparable selective ultrafilters and $2^{< 2^{\mathfrak{c}}} =
2^{\mathfrak{c}}$, we obtain torsion-free topological groups with respect to
Comfort's question on the countable compactness of (infinite) powers of a
topological group.
