Fieldset elements produce double links

Drupal seems to produce two links for collapsible forms in the legend element. The situation looks like this:

<legend class="collapse-processed">
<a href="#"/>
<a href="#">Some legend</a>
</legend>

This behaviour does not seem strange for the user as long as you don't set e.g. bottom padding for link elements. Doing this visualizes the "anchor" link above the actual link that's used for collapsing the element (see attached screenshot).

Tested on three different Drupal installations with default and custom themes. Behaviour can be reproduced by looking at the modules page (admin) and the fieldsets there.

Any idea why Drupal renders fieldset elements like this? Disabling the empty links through js helps, but is not a very elegant solution. Disabling those links does not break collapsibility.