Thanks for your suggestions.
I could write a script that checks for user posted flags in comments and sends me a notification to check that deal. good idea.
Concerning the whitelist, for now I think I'll wait and see how things go. Hive users are already used to getting downvotes for spam which results in no rewards. If things get worse I can add it later. At the start it seems to be too limiting to add a whitelist, especially with a worldwide community.