This seems ok, at least doesn't break anything obvious when I test locally. It seems it's introducing three new concepts - encapsulation, legend, prohibited, although the subject just mentioned prohibited. But presumably it's clean enough to treat them together.

This is a draft pull request, so I'll just approve for now, can merge once it's marked ready for review. Pull 985 in aria seems to have redundant changes, I assume it's cleaner to remove the changes in "common" from that pull request, as they'll come in when the common directory is updated upon merge of this pull request.