Fix: Minor display issues in IE 11

ie-fixes.css

/* IE fixes */
.main-navigation li.menu-item-has-children > a:before,
.main-navigation li.page_item_has_children > a:before,
.main-navigation .sub-menu li.menu-item-has-children > a:before,
.main-navigation .children li.page_item_has_children > a:before {
	display: none;
}

.main-navigation li.menu-item-has-children > a:after,
.main-navigation li.page_item_has_children > a:after {
	content: "\25bc";
	position: relative;
	top: -0.25em;
	font-size: 0.45em;
	padding-left: 6px;
}

.main-navigation .sub-menu li.menu-item-has-children > a:after,
.main-navigation .children li.page_item_has_children > a:after {
	content: "\25b6";
}

.page-header.has-post-thumbnail {
	text-shadow: none;
}

.page-header.has-post-thumbnail .page-title,
.page-header.has-post-thumbnail .archive-description {
	text-shadow: 0 1px 1px rgba(0,0,0,0.4);
}

Hi! Thanks for letting me test this first. I didn't do full-scale testing, but the arrow positioning is fixed where it was a problem before. Same with the text cutting off in the panel paragraph.

I was still seeing the link hover jumping (per the video), but I think I've isolated it to line 96-97 in the main parent css. If I change:
a:active, a:hover { outline: 0; }

to just
a { outline: 0; }

Then the problem is fixed. I'm not sure if that's going to conflict with your other styles, so if you'd rather let that one be I can just override it in my child css.

Will you be rolling out these changes to the theme on wp.org, or should I keep these styles in my child theme for now?