In users form, on site view, I use the "user avatar" field (uplaod image type). It's a default field I founded in User Profile app folder. I use the default configuration : thumb1 - storage : standard - article - avatar.
To display this avatar in user's profile, no problem.
In my comments list and search, I use custom template position (seb minima template). I use articled created by field in item view to display the author of each comment. I try to use in this same view my avatar field (I call it in my custom template with <?php echo $cck->renderField('user_avatar');?>) but it's not displayed.