if you display each user’s post count under their username, then people are going to start posting a lot. If you implement a karma score, then people will try and do things that maximize karma. Not only [is] exposing information about valued work important, not exposing information can also be an important design strategy.
– Xianhang Zhang
If players have achievements they can see, many will go out of their way to get them, and a subset has gotta catch them all. If you let other players see what achievements they have finished, you will see more achievement-seeking. If you only (or more easily) show how many achievements people have completed, they will tend to get the easy ones to drive up that count. If you add varying points for each achievement, you will see min-maxing based on the difficulty-reward of achievements, with forum posts on how achievement x is too easy/difficult for its reward.
In The Lord of the Rings Online™, you cannot see how many deeds someone has finished, only their equipped traits. You should expect to see people polishing the virtues they equip and ignoring the ones they do not, because both function and style reinforce that. You cannot see someone’s crafting ranks, but when they added auto-generated forum signatures, crafting ranks were listed on there. I don’t suppose that anyone has the data, but I would expect to see a bit more crafting done after that point, particularly for people more active on the forums (and using the character signatures).
We will also expect some counter-culture blowback: people who do no crafting or avoid achievements specifically so that they have 0s. They just need some way to signal “I am a conscientious objector” rather than “I am a scrub.”