Obsolete Pattern "legend" #1259

We currently have an issue in Plone where pat-legend leads to form-tabs not being displayed anymore. Plone has it's own logic to transform fieldsets to tabs which also uses legend elements for the tab headings (IIRC).

pat-legend changes all <legend> elements to <p class="legend"> ones.
I wonder why we do this.

What is pat-legend used for? Is it still necessary?
If we don't need it, I'd suggest to remove it.
If we do, I can still use a BLACKLIST feature in Patternslib to exclude that one pattern.

This is how in Plone the form-tabs look with pat-legend in place:

This is how it should look like instead: