I am also experiencing the duplicate comments bug. My understanding is like this. SNAP pulls comments from Facebook every hour on a recommended but set 10-20 posts.
I’m getting the same comment duplicated and put under my posts. Sometimes three of the same post in a row.
I looked for hours trying to solve this. I searched for “block duplicate comments WordPress” and much more but was unable to fix this.
The dirtiest method is something like creating a php script to delete duplicated comments from the database. Then I imagine If I implemented that I’d setup a cron job to run it every hour. The dirty part is that once it cleared out the duplicates, what if a duplicate had a reply to it? What it the cron trick was constantly fighting with the plugin?
Looking forward to a legit fix from NextScripts on this. As for now I’m just letting the plugin duplicate the Facebook comments in WordPress.