And where is it stated/implied that you are limited to one counter feedback per account? (I'll remove it if this is the case, however I do not know of any limitation)
I doubt it is stated anywhere, but it certain is implied...
The feedback was already countered. You are basically stating you trust Anduck and you do not trust me., when in your words we were both guilty of the same thing.
If a person can be tagged by multiple people for the same reason, such as a single scam instance or by being a scam buster, I don't see why multiple counters for one feedback shouldn't be allowed.