bridgy supports u-photo for publish (POSSE): https://brid.gy/about#picture

and backfeed: https://brid.gy/post/twitter/schnarfed/831552681210556416 . simplified markup snippet:

<article class="h-entry">
  <span class="p-author h-card">
    <a class="p-name u-url" href="https://snarfed.org/">Ryan Barrett</a>
    <img class="u-photo" src="https://pbs.twimg.com/profile_images/459041662707060736/Kb9Ex4X8.jpeg" alt="" />
  </span>
  <div class="e-content p-name">
  💯💯💯 (by <a href="https://twitter.com/itsmaeril">@itsmaeril</a>)
  </div>
  <img class="u-photo" src="http://pbs.twimg.com/media/C4pEu77UkAAVy9l.jpg" alt="attachment" />
  ...

The WordPress Semantic-Linkbacks Plugin (webmention) is supporting u-photo in h-cards for avatars. The h-entry photo is not handled by a WordPress plugin yet.

Aperture consumes the u-photo property on posts. All 3 current Microsub clients (Monocle, Together, and Indigenous) also consume the property to display photos in the reader interfaces.

Verified markup on many examples from https://indieweb.org/photo#IndieWeb_Examples as of today:

• https://sixtwothree.org/photos/1
• https://martymcgui.re/2016/04/28/133049/
• https://gregorlove.com/2015/08/i-found-some-silers/
• http://tantek.com/2015/244/t1/did-entire-npsf-trackattack
• https://kartikprabhu.com/notes/dusty-rhodes-watershed
• https://calumryan.com/note.php?noteId=115
• https://adactio.com/notes/6978/
• https://aaronparecki.com/2014/05/06/12/iiw-indieweb

We need to, for the sake of this proposal, define u-photo. The wiki's draft definition is:

u-photo - one or more photos that is/are considered the primary content of the entry, unless there is a p-location h-card, which is still considered a "checkin" (i.e. with a photo). Otherwise the presence of a u-photo means the name of the entry should be interpreted as a caption on the photo, and the summary/content should be interpreted as a description of the photo.

The statement about p-location h-card needs to be clarified? Should this be part of the definition of the property or should it read, "One or more photos that is/are considered the primary content of the entry. The presence of a u-photo means the name of the entry should be interpreted as a caption on the photo, and the summary/content should be interpreted as a description of the photo." When other properties change interpretation seems a matter for Post Type Discovery.

At the Microformats session today, it was decided by consensus that there were additional items that needed to be addressed, #23 and #24 prior to moving this property to core.

It seems to me that u-photo is inconsistently defined. For h-recipe, it is merely "an accompanying image," whereas for h-entry it is "one or more photos that is/are considered the primary content of the entry...."

I suppose the thinking is that if an h-entry is not primarily a photo, there's no need to add a specific class name to a photo. But why is there such a need for h-recipe? It appears that the point is to specify a featured image. Yet for h-entry, the author specifies a featured image with u-featured, which indicate "a representative photo or image for the entry...."

I think this inconsistency could be confusing for authors.