app_container: Expand TODO

app_containers/.local/bin/run_app_container

@@ -80,6 +80,8 @@ if [ "$CONTAINER_USE_USERNS" = true ]; then
   bind_opts="idmap"
   user_on_host=$((private_users + run_as))
   # TODO: DBus is broken inside a user namespace due to permission issues
+  #       And in fact, in any case when the UID inside the container does not
+  #       match the one on the host.
   # TODO: Fix this, somehow.
 fi