After moving a site to AdaptiveTheme, I found the tags in the date created for comments were not being read properly.
What was output in the source code was
<a rel="bookmark" href="/comment/9999#comment-9999"><time pubdate="pubdate" datetime="2012-08-07T14:02:22-04:00">Tue, 2012-08-07 14:02</time></a>
After trying to find the route of my issue in the AdaptiveTheme code, I found the issue was that I had "Alter publication date markup" checked at /admin/config/development/html5-tools because the previous theme didn't have this feature built in.
I just thought I'd mention it here, in case anyone else is running into this issue and looking for a solution. Perhaps there could be a note in the documentation for this module or in the description itself:
Alter publication date markup
Implements the new element and it's pubdate attribute, altering content and comment publication dates with the new HTML5 format by overriding the $submitted variable. This could cause issues with Genesis, AdaptiveTheme and potentially with other themes.