The current default implicit ARIA semantic for <aside> is "note". See section 184.108.40.206 Implicit ARIA Semantics .
It is proposed that this be changed to "complementary" for the following reasons:
A. The definition of <aside>  seems more closely aligned to the definition of
the "complementary" role  than it does to the definition of the "note" role , particularly with regard to the element's content still being meaningful when separated from the surrounding content.
B. Firefox/Win and Safari/Mac, the only two browsers currently mapping additional semantics for <aside> to the accessibility APIs, both map it to the "complementary" role, Firefox/Win using an IA2 "xml-roles" object attribute and Safari/Mac an AXSubrole of AXLandmarkComplementary.
C. The HTML to Platform Accessibility APIs Implementation Guide advises that browsers map the <aside> element to the "complementary" role where the accessibility API permits .
I'd be happy to change this. What do other a11y experts say about this?
(In reply to comment #1)
its already been done
EDITOR'S RESPONSE: This is an Editor's Response to your comment. If
you are satisfied with this response, please change the state of
this bug to CLOSED. If you have additional information and would
like the Editor to reconsider, please reopen this bug. If you would
like to escalate the issue to the full HTML Working Group, please
add the TrackerRequest keyword to this bug, and suggest title and
text for the Tracker Issue; or you may create a Tracker Issue
yourself, if you are able to do so. For more details, see this
Change Description: No Change
Rationale: Already fixed (thanks Steve!)