Note that the initial request does use angle brackets, which I assume is the intended way.
Accept-Profile: <http://example.org/profile/x>
Please ensure consistency throughout the document on the use (or lack) of angle brackets in profile HTTP headers.
Example 4, for instance, does use angle brackets for the Accept-Profile HTTP header.
Example 5 of https://www.w3.org/TR/2019/WD-dx-prof-conneg-20191126/ shows a response that states the profile without angle brackets:
Content-Profile: http://example.org/profile/x
Note that the initial request does use angle brackets, which I assume is the intended way.
Accept-Profile: <http://example.org/profile/x>
Please ensure consistency throughout the document on the use (or lack) of angle brackets in profile HTTP headers. Example 4, for instance, does use angle brackets for the Accept-Profile HTTP header.