I saw that Ponder was moved out of beta just a few hours ago so thought it would be OK to make a task for this.
1. Navigate to Ponder
2. Select Edit Query
3. Update query to only have the "Answered by" filled out with a user
The results appear to not be filtered to show only questions that have been answered by the selected user. Example:
https://secure.phabricator.com/ponder/query/_ya_4qHDHeyJ/#R
Additionally I wasn't sure if intended or not, but it appears as though not-logged-in-users can view the list of questions, but are prompted to login when viewing a specific question.