One question though: Say an operator/service provider is managing several ANNs in different languages. Obviously it would be important for them to track the traffic they are getting from the local boards. Would this be okay or still forbidden?
I think it would be ok. I seen lot of services using tracking tags in their links. First example which comes to my head is Freebitco.in, but we can easily found lot of other services. This is how their link in ANN looks:
http://freebitco.in/?r=4&tag=bitcointalk.
So, for services such links is allowed.