I just set that up a bit ago and basically created a new group based on registered users.. all i did was turn on akismet for the first group and turned it off for the second promoted group.
i ran the task and had promotions updated, i checked the groups to ensure the proper users were in their primary promoted group (which they were).
Now when the plugin is enabled I have promoted user group users getting filtered by the plugin, how is that possible? The users in question are clearly in the promoted group and that group has AKismet filtering off...