While I understand that it is possible to use

text.usetex = True

along with the appropriate declarations for text.latex.preamble to be able to use \boldsymbol, it would be nice to be able to keep

text.usetex = False

with something like

title(r'$\boldsymbol\psi_N$=0.95')

to achieve bold symbols.

Even better would be to detect whether the current font is bold, and automatically substitute in a \boldsymbol command.

(As always, I'm appreciative of the work that matplotlib developers have contributed, but I also know that the squeaky wheel gets the grease.)