Assuming there are no Validation errors, the resultant html will be injected from a call to @Html.ValidationSummary
<div class="validation-summary-valid" data-valmsg-summary="true"><span>...</span>
<ul><li style="display:none"></li>
</ul></div>
and assuming you have the standard validation-summary-valid in your css (display: none;) the div will not be shown.
Thats fine but wouldnt everything work the same if @Html.ValidationSummary("...") output nothing instead of a ‘hidden’ div?
If the unobtrusive jquery functions are going to populate the validation summary client side, would the scripts not need a place to put the summary? Otherwise, you would have to reload the page each time and that defeats the purpose of client-side validation.