WYSIWYG has 2 levels of bold: one introduced by Flamingo's heading and the standard one (<strong>)

Reported by Eduard Moraru:

There's a problem in wysiwyg caused by flamingo's default font-weight of 500 (instead of 400) that practically sets headings to bold by default.
http://ci.xwiki.org/job/xwiki-enterprise-test-wysiwyg/lastBuild/org.xwiki.enterprise$xwiki-enterprise-test-wysiwyg/testReport/org.xwiki.test.wysiwyg/StandardFeaturesTest/testBold/
this test does the following:

        typeText("x");
        applyStyleTitle5();
        selectAllContent();
        clickBoldButton();
        assertContent("<h5><strong>x</strong></h5>");

so bold is set by default now when applyStyleTitle5(); is done
when clicking bold again, wysiwyg tries to reset flamingo's default bold, so the content ends up being wrapped in

<span style="font-weight: normal;">x</span>

and the bold button is now unset
if bold is pressed yet again, rendering (this time) wraps the content ( x ) in a strong element (as expected), but inside that span, ending up with:

"<h5><span style="font-weight: normal;"><strong>dsadsadsa</strong></span></h5>"

default font-weight is 400, bootstrap/flamingo uses 500 for headings and WYSIWYG's inserted <strong> is 700.

should we override bootstrap into using font-weight 400 for headings, like colibri was doing? Any other suggestions?