Hmm – you shouldn’t need to change the stylesheet in order to get the Genericons showing.
I installed a fresh copy of Canard 1.0.6 on my test site and both the social icons and search icon are showing correctly.
Have you made any modifications to the theme files directly, instead of using a child theme or custom CSS plugin to isolate changes?
This is how lines 258-287 of style.css should look. Note that there is no reference to Open Sans or the other fonts in your code above, only Genericons:
/*--------------------------------------------------------------
# Genericons
--------------------------------------------------------------*/
blockquote:before,
.back-top:before,
.comment-navigation .nav-next a:after,
.comment-navigation .nav-previous a:before,
.dropdown-toggle:before,
.main-navigation .menu-item-has-children > a:after,
.menu-toggle:before,
.posts-navigation .nav-next a:after,
.posts-navigation .nav-previous a:before,
.search-form:before,
.search-toggle:before,
.sidebar-toggle:before,
.social-navigation a:before {
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
display: inline-block;
font-family: Genericons;
font-size: 24px;
font-style: normal;
font-weight: normal;
height: 30px;
line-height: 1.25;
speak: none;
text-decoration: inherit;
vertical-align: top;
width: 30px;
}
If you did make changes directly to the theme files, please keep in mind that all your changes will be overwritten and lost every time the theme is updated to the latest version.
An easy way to add custom CSS is to install the Jetpack plugin and activate the Custom CSS module. You’ll then add your custom CSS in the new stylesheet editor that’ll appear in your dashboard, under Appearance > Edit CSS.
As alternatives, you could either install a standalone custom CSS plugin, or create a child theme. A child theme is also necessary if you need to make any changes beyond just CSS.