On my site I have events that have like buttons, the prefilled FB details are correct, but below that when you attempt to add a comment it post to your timeline as expected but with the wrong event details.
Here's an example:
There you will see a comment I posted but it appeared on Facebook with details from a completely different post_id. (I'd include photo but don't see option to).
Please help, I'm positive this is why many users have been discouraged to use our comments