There is currently no placeholder text in the search field in Minerva on mobile. It looks like the placeholder value in the <input> tag is currently blank:

<input class="search" type="search" name="search" autocomplete="off" placeholder="" value="">

For consistency as well as brand awareness I think it would be good to add the standard "Search Wikipedia" placeholder text back in here.

Developer notes

The placeholder shows up on tablet but not on mobile.
The problem is openSearchOverlay gets the placeholder from

$this.attr( 'placeholder' );

but $this in the context of mobile refers to the search button which has no placeholder. It should always be sourced from the input element. There is also no reason to get inside the event handler. It never changes.

	function openSearchOverlay( ev ) {
		var overlay,
			$this = $( this ),
			searchTerm = $this.val(),
			placeholder = $this.attr( 'placeholder' );

$( '#searchInput, #searchIcon, .skin-minerva-search-trigger' ).on( 'click', openSearchOverlay )