I know what you mean. I can say it is wonderful, when it is sincere: when the follower does it in special moments, when she really feels like it.What I learned as "active following" is what one of my teachers calls "er"-ing your leader. Ie, if he leads small- go smaller. If he leads big- go bigger, soft, go softer, etc... In other words, take his lead and fully go with to its natural conclusion and really participate in the motion, not just let yourself be "placed" everywhere.
It can become annoying if done costantly at every step.
If you don't really think that in this moment your step should be soft, there is no point that you do it softer than me!
Moreover, sometimes the leader just wants you to do a step of a given degree of softness, or lenght: nothing more and nothing less. Maybe a larger step will bring you too close to the next couple and shorter step wouldn't allow to do what he has in mind.
In general, I'd say that as a rule of thumb the two partners can't be active at the same moment, because it would mean that they are dancing alone: when one of them is active, the other one is listening.
So, adornos are welcome, like active following, and hijacking. But remeber that in those moments it's like if you temporarily take the lead: you can't do that continuously...