There's a bug in the v5.1.1 release where the filters options aren't properly shown. To fix, go to the Content Plugin - Like area in the Social section and:
* Set the buttons to display in a category view (top, bottom, both, it doesn't matter).
* The filters will display at the bottom of the category section
* Set the filters how you want (exclude the specific article IDs to exclude)
* Then, set the buttons to no longer display in the category view (none)
In other words, the filters are still there and work, but the filters are only incorrectly shown in the category section.
The filters will be fixed in the v5.1.2 release to always show. That release will hopefully be out late this week.
Thanks,
Alex