Hi,

Unless I am mistaken, +strike-through+ markers in headings cause the
heading face to disappear.  To reproduce, in an Org buffer, add the
following heading:

    * foo *bar* /baz/ _quux_ +corge+

Testing this with emacs -Q, on commit f9694a7 of the master branch,
bar (resp. baz and quux) displays the org-level-1 face as well as the
bold (resp. italics and underlined) decoration, but not corge: the
latter only shows the strike-through decoration, not the header face.

I poked at org-do-emphasis-faces with the silly patch attached, and
the issue went away (corge shows both the header face and the
strike-through decoration).