nxml-char-ref-display-glyph-flag

nxml-char-ref-display-glyph-flag is a variable defined in `nxml-mode.el'.
Its value is

t

Documentation:
Non-nil means display glyph following character reference.
The glyph is displayed in face `nxml-glyph'. The abnormal hook
`nxml-glyph-set-functions' can be used to change the characters
for which glyphs are displayed.

You can customize this variable.