Forwarding a report in ca.wiki:
When two users are trying to post a comment at the same time in a Flow page, both get this confusing error message:
You have not sufficient permissions to perform this action
In this case both users were ol' vets, and soon they figured out what was happening (a conflict of edits). Regular users will get surely puzzled by this message.
A message explaining why your comment isn't posted yet, and what needs to be done to publish it.