For a rotating Kerr black hole, it can be shown that the possible absolute value of its angular momentum is bounded by its mass squared

\[¦ J¦ \le M^2\]

where equality means that we have an extremal black hole.

What is the intuitive interpretation of this constraint of the angular momentum for both, microscopic and macroscopic (astrophysical) black holes?

From my naive hand-waving understanding, I could imagine that in case of an astrophysical black hole, it just means that a too large angular momentum would tear the black hole apart.

However, concerning microscopic black holes (with a mass about $m_p$) I have not much intuition about what this upper bound for the absolute value of the angular momentum could mean. By some S-duality arguments, such a microscopic black hole corresponds to lowering the string coupling constant to a single elementary particle, so there is nothing that could be torn apart by increasing the angular momentum for example.