There should be a notification when a moderator reviews or looks at a post which you've flagged.
The notification could show the status (helpful, declined, disputed, or something else) of your flag.
Edit
The reason for doing this is so that you would be able to see when a post which you have flagged has received moderator attention, at which point you could go back to the post. This would be good, for instance, if:
- you flagged a post for migration to another site; after migration occurs, you could answer the question, since the FAQ suggests that only unanswered questions should get migrated
- you flagged a post for removal of spam or otherwise nonconstructive content, and the content removal has to be carried out in batches