This seems to be a conflict with the Oslo template. If you switch to Seattle, it goes away.
I was able to work around it by editing the forms in Designer 2013. You'll want to make the same edit on each of displayifs.aspx, editifs.aspx, and newifs.aspx.
Find this section near the top:
<asp:Content ContentPlaceHolderId="PlaceHolderPageTitleInTitleArea" runat="server">
<span class="die">
<SharePoint:ListProperty Property="LinkTitle" runat="server" id="ID_LinkTitle"/>
</span>
</asp:Content>
Change it to this:
<asp:Content ContentPlaceHolderId="PlaceHolderPageTitleInTitleArea" runat="server">
<span class="die">
<SharePoint:ListProperty Property="LinkTitle" runat="server" id="ID_LinkTitle"/>
</span>
<style>
#sideNavBox { DISPLAY: none;visibility:hidden; }
#contentBox { margin-left:auto; margin-right:auto; }
</style>
</asp:Content>
update - The > was missing off the end
#contentBox { margin-right:20px;margin-left:220px; min-width:703px;}
How can I edit it?