Problem/Motivation
Based on The W3 spec, forms that use an asterisk to indicate required fields should include a text description explaining what that asterisk means. For example, this text is not present on node/add/page, a form that certainly has required fields indicated by an asterisk on their label. This criteria can also met with text describing the asterisk at the beginning of the form, or by adding "(required)" to the label. Deque also has a concise description of this criteria and how it can be met.
Steps to reproduce
Create a form with at least one required field.
The required has an asterisk, but the meaning of the asterisk is not explained.
Proposed resolution
Adding an explanation at the beginning of the form is probably the easiest way to fix this.
Another solution would be to add (required) at the end of each label but I think this would be a breaking change.
For example, some websites already added this information into their label manually so it would duplicate it.