Case 1: your flag was helpful, but nothing happened. Causes include:
- An edit or other action that occurred between your flag and the moderator reviewing it meant that moderator action wasn't required. However the moderator felt you were right at the time of flagging, and so marked your flag helpful to reward/encourage you.
- Your flag was borderline, and the moderator felt it wasn't a bad enough post to act on it, but wanted to let you know you weren't exactly wrong.
- Flags to close a question will be dismissed as helpful as soon as another user votes to close it. However, if you don't have enough reputation to see close votes, it will appear as if nothing has happened until more users vote to close and the question is actually closed.
- Your "not an answer" or "very low quality" flag was reviewed by normal users who recommended deleting it, which marked your flag "helpful" as the post was initially deleted ("from review"). However, later, the author manually undeleted it. This may later look as if your flag was marked "helpful" without it being deleted. To verify this, check the post's revision history. If this is the case, and the problems have not been solved, cast a custom moderator flag, as a moderator's deletion will prevent the author from undeleting it again. NAA and VLQ flags are also marked helpful when the post's owner deletes and undeletes it. Additionaly, any edit will resolve VLQ flags as helpful.
Case 2: Your flag was declined, but exactly what you wanted to happen happened (e.g. the post was deleted). Causes include:
- A moderator disagreed with you and your flag was declined. Later, other people agreed with you and also flagged, and a second moderator who saw their flags agreed with them and took action.
- The flag reason was wrong, but the post still had issues that would cause action to be taken. Because the review queue uses flag metrics for its baseline, it is important that flag reasons match why action should be taken against a post. Examples include flagging an answer as "very low quality" when it's not entirely unsalvageable, but it makes no attempt to answer the question (i.e. "not an answer").
- If your flag was a recommend closure flag, if it receives three "Leave Open" responses in the Close Votes queue without a single close vote, it will be marked declined. When you flagged, this is what happened, but later others decided that the question was worthy of closure and therefore closed it.
Alternate explanation that applies to either case: a moderator clicked the wrong button by mistake and it's not a big deal. For genuinely bad posts, other people flag them too, so they end up solved.