If you give a group a description and use the list BBCode, the layout breaks when viewing the group page (memberlist.php?mode=group&g=3) 

This is because the group description is wrapped in a <p> but it should ideally be in just a <div>

Original code in memberlist_body.html template:

        <p>{GROUP_DESC} {GROUP_TYPE}</p> 

Could be:

        <div class="content">{GROUP_DESC} {GROUP_TYPE}</div> 

Note: content has a smaller font size than <p> so a different class and a possible a CSS edit would be needed to replicate the look of the original.