excellent! WP-GNU social plugin is working like a charm :-)

"WP-GNU social is a !GNUsocial based comment system. After installing and configurating the plugin, evey new post will start a new conversation in your GNU social node. The conversation will be displayed and locally saved as usual wordpress comments in your blog. Everybody with an user in a node with someone subscribed to your GNU social user (i.e. your node) can comment your post directly from its own GNU social node."

https://wordpress.org/plugins/wp-gnusocial/