Post to Group as Facebook user - not channel owner?

There isn't a way to change this. Facebook requires the channel to be setup and permission granted from a user that will do the posting to the Group. All automated posts come from that user because they are the only ones that have granted the manage_groups permission on authentication. All the other users on the site (even admins) aren't asked for that permission unless you setup a channel specifically for them and then they use the "Create Post" link in the social toolbar to manually post the message instead of using the automated posting option.

I hope that helps explain, but if you need anything else, please let us know.

Thanks,
Alex

Just to confirm though, if I set up second channel, for instance for my Italian admin, and assign that channel owner to his user, then when he logs on and manually 'Creates a Post', this will be posted as him without any other action?

Yes.

The 'Create Post' manual option has checkboxes to pick a channel. The post will be from the chosen channel's owner to that channel's group/page/etc. Whether you or the Italian admin log in on the front-end, if the second channel with the Italian admin owner is enabled for the post, then post will go from the Italian admin since he/she owns the channel.

-Melissa