I've had several flags declined with: "Moderator did not find any evidence" - mostly because I've flagged link-only answers as NAA - and the author has edited the post before the flag was reviewed, and then the flag became invalid.
Do you have any suggestion for this - or is it simply not an issue that some flags are declined this way? It's not a problem for me, so if everyone thinks this is the way it should be - no worries. 😎
I think that non-mods cannot do much regarding this. But mods should be a bit more careful when handling flags. I think that mods can also see who the user that flagged a post is, so they could have a second look at a post that seems OK but was a flagged by a user like you, who has a significant amount of helpful flags.
Also, an idea that just came to me, is that it would be nice if we could also have a flagging badge, that would be also be shown to mods when they are handling flags, so they could more easily know if the user that has flagged a post has a positive flagging history, thus their flags are a bit more reliable.
Regarding you having a few declined flags, I think that it's not a major issue, since it's unlikely that you will have a lot of flags declined in the same time period, giving you any restrictions. But you may see a warning for a few days in the flagging dialog saying that you should be more careful because you recently had declined flags, which is a bit annoying.
