This suffers from the N+1 Query Problem. Although it's not a big deal, it's easy to fix. A cleaner approach (which makes a single service call in the worst case, and thus performs better) would look like this:

$other_author_phids = array();
foreach ($revisions as $revision) {
  if ($revision['authorPHID'] != $this->getUserPHID()) {
    $other_author_phids[] = $revision['authorPHID'];
  }
}

$other_authors = array();
if ($other_author_phids) {
  $other_authors = $conduit->callMethodSynchronous(...);
  $other_authors = ipull($other_authors, 'userName', 'phid');
}

This also avoids the service call entirely in the common case.

In the output, let's not show anything special if the user is the author, and preface the revisions if they aren't to make it easier to see the author annotation. With the current approach, it can get lost at the end of a long line. For example, if the user owns D123 but not D124, output something like this:

D123 Add feature
D124 (alincoln) Add other feature