> This also happens with the xkcd plotting style using the "Humor Sans" font.

So uh, this is why #26854 is failing (the plt.xkcd examples seem to work because they don't have a negative in the labels anywhere): throws "glyph missing" warning for title, omits hyphen for ticks:

Originally posted by @story645 in #17007 (comment)

per the discussion downthread, if a font does not have a designated .notdef then the missing glyph character (the .notdef) is not rendered.

Suggested Fix

For this one character, we should have a fallback such that we always render some glyph when a glyph is not found. This is particularly because of situations like the missing - at the front of a text, where it may be easy to miss that it's missing.