The window's display table, if there is one, takes precedence over the
buffer's display table. If neither exists, Emacs tries to use the
standard display table; if that is @code{nil}, Emacs uses the usual
-character display conventions (@pxref{Usual Display}).
+character display conventions (@pxref{Usual Display}). (Emacs does
+not ``merge'' display tables: For instance, if the window has a
+display table, the buffer's display table and the standard display
+table are completely ignored.)
Note that display tables affect how the mode line is displayed, so
if you want to force redisplay of the mode line using a new display