A low-quality post appeared in the flag queue and I clicked the "flag" button to reinforce it. Only after doing that did I realize that I could just cast a delete vote instead. Mine was the third vote, so that deleted the post. I felt bad about the now-obsolete flag that I couldn't withdraw, and out of curiosity looked at my flag history to see if the system had been smart enough to auto-resolve it.
It did. That's good. It also marked it as helpful.
Should that have happened? It's probably not a big deal (how often does the situation come up, and do we really care about a few "bonus" helpful flags on the way to Deputy and Marshal?), but it seemed odd to have, essentially, resolved my own flag.
I don't think a flag in this case should be declined (there was a problem, after all, and we don't want to mis-train the Community flagger), but perhaps, as with comments that are deleted by their owners before the flag is handled, there should be an intermediate "obsolete" state?