This is a great plugin. Thanks for sharing it with the community.
I have a request that I think will make it even better.
To make use of the social comment feature for site visitors, we have to allow anonymous comments in the WP settings. That is to say Settings > Discussion > "Users must be registered and logged in to comment" must be unchecked. If it's checked, visitors cannot comment using their social media accounts via the Social plugin because WP requires them to be logged in via a WP account.
In the scenario above, the WP site obviously receives a lot of comment spam. This requires an additional spam fighting plugin or requires someone spending a lot of time moderating comment spam.
A couple of solutions come to mind.
One option is to add a filter in lib/social/comment/form.php that allows one to modify the form output so that a challenge question can be added.
Knowing the first option could be tricky and some devs could break the plugin, another solution is to add an option in the plugin settings that allows site admins to specify, if they want, a challenge question to be displayed.
Either of these would significantly reduce the comment spam that comes in from bots auto-filling the default fields.