Whenever I mark a flag as invalid my 'disputed' count raises. This feels kinda wrong as I'm helping the moderation to recognize invalid flags (most of them caused by auto-flagging). I'd expect the 'deemed helpful' count to raise instead.
There are three separate categories of flag outcome: helpful, declined and disputed. If you dispute a flag, or if a flag of yours is disputed, then both the disputed flag and the “disputed” flag are in the disputed category, whatever the moderator ends up doing with the flags.
Disputed flags have no effect on either flagger's flag weight.
The disputed status for flags means simply that there were different opinions about this post - i.e. one person flagged a post as something, and someone else flagged this as "invalid flag".
Independent on what the moderator later says, the flag will show up in your list as "disputed", and neither your flag weight not that of the other person will be changed.
Disputed thus does not mean that a moderator disagreed with your flag (that would be "Declined"), but simply that there were different opinions, nothing to worry about.
I don't know if this is a good idea to handle the "invalid flag" flags (and the original flags).
So, when I have the same opinion on the validity of a flag as the moderator that comes after me, I in effect work against the flag weight algorithm by eliminating the effect of bad flags on the flagger's flag weight, so the same flagger can go on issuing bad flags.
On the other hand, if I were malicious or had other opinions than the moderators on which flags are valid, I can simply eliminate the effect of good flags on the flagger's flag weight, also sabotaging the flag weight algorithm ... without any effect on my flag weight, too.
Is this really what was intended with the "invalid flag" flag type?