There was a bug in 6.x, where comments could post twice upon clicking the submit button on the ajax comment form.
I have occasional cases of users having comments posted multiple times in 8.x version of this module too. I did not find a reproducible process to make this bug happen yet but will edit this issue if I manage to.
Active
Code
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
It seems like the issue with comments posting multiple times has persisted into version 8.x, though it's less frequent and harder to reproduce. If you manage choiceadvantages to identify a reproducible process, it would be helpful to document it for further troubleshooting and to potentially resolve the bug.