Index: src/routes/posts.js
===================================================================
--- src/routes/posts.js	(revision 55bc7f95d6ee2d94bdaba55d6ca87265e217dbc4)
+++ src/routes/posts.js	(revision 52ea6df4abea1a346a912f9f11d8e52a474df932)
@@ -753,4 +753,6 @@
   // Owner/admin of this site may reply back to a fediverse interaction.
   const canManageSite = !!(req.session?.user && PermissionsService.canAdminSite(req.session.user, site));
+  // Avatar for our own (outbound) fediverse replies = the site's profile photo.
+  const siteAvatar = (site && site.profile_photo) ? site.profile_photo : null;
 
   renderPage(req, res, 'pages/post', {
@@ -763,4 +765,5 @@
     fediverse,
     canManageSite,
+    siteAvatar,
     likeCount,
     likedByMe,