You have to go in the productcomments.js file of productreviews (can be found in your theme or module directory under the js folder) and change this:
$(document).on('click', 'a[href=#idTab5]', function(){
var target = this.hash,
$target = jQuery(target);
jQuery('html, body').stop().animate({ 'scrollTop': $target.offset().top - 180 }, 500, 'swing');
$('*[id^="idTab"]').addClass('block_hidden_only_for_screen');
$('div#idTab5').removeClass('block_hidden_only_for_screen');
$('ul#more_info_tabs a[href^="#idTab"]').removeClass('selected');
$('a[href="#idTab5"]').addClass('selected');
});
To this:
$(document).on('click', 'a[href=#idTab5]', function(e){
e.preventDefault();
e.stopImmediatePropagation();
var target = this.hash,
$target = jQuery(target);
jQuery('html, body').stop().animate({ 'scrollTop': $target.offset().top - 180 }, 500, 'swing');
$('*[id^="idTab"]').addClass('block_hidden_only_for_screen');
$('div#idTab5').removeClass('block_hidden_only_for_screen');
$('ul#more_info_tabs a[href^="#idTab"]').removeClass('selected');
$('a[href="#idTab5"]').addClass('selected');
});
Done!