Matplotlib version 2.0rc2
installed via conda install -c conda-forge/label/rc -c conda-forge matplotlib

As per the image below, a subscript g is truncated when combined with a superscript. In the example, the Greek Sigma may be any other letter:

import matplotlib.pyplot as plt

plt.title(r"superscript '-' truncates subscript 'g'        $\Sigma_{g}^{-}$")

plt.savefig("truncated-title-subscript.png", dpi=75)
plt.show()