In end-user (public, non-authorized user) themed output, groups of Children nodes and Link Operations are wrapped in FIELDSETs with LEGENDs. However, the content within these containers are not form elements -- it's text and HTML output.
This is a completely inappropriate use of these containers that significantly complicates styling via CSS (particularly in the case of LEGEND). It also violates the HTML 4 and XHTML specifications, which require that FIELDSET and LEGEND be contained within a FORM and be solely used "to group thematically related [form] controls and labels".
This inappropriate use of FIELDSET and LABEL also poses accessibility issues that could easily confuse users of assistive technologies.
This default themed behavior should be removed altogether. It should not even be an option. Instead, DIVs should be used.
Behavior present in versions 5.x-2.2 and 5.x-2.x-dev.
(To be clear: this applies only to end-user themed output. Use of FIELDSETs and LEGENDs *is* appropriate within the admin tools.)