I don’t think post count is an interesting metric; I had some other ideas:
I need to know when this person is around? Tell me when this person is most likely to post based on statistics, what day of week, what time of day. Ideally a graph like we did on chat.stackexchange. So for Tim Post http://chat.stackexchange.com/users/224/tim-post we can see that he’s most likely to post on Wed, Thu, Fri around 06:00 to 16:00 hours.
This would cover “last seen”. Doesn’t need to be a full bore graph, just some basic text like “tends to post Wed, Thu, Fri from 3pm to 11pm your time”. Now you know when this user will be around based on participation data. (I think we have to base this on posts, otherwise it gets weird.)
I need to know who this user is? Show my previous interactions with the user, because, “it’s all about me”. Display this user’s recent replies to me (quotes and post replies and @name mentions), any recent PMs I had with this user, and a total count of likes to and from this user. Me me me me me. What’s my prior history with this user? What did we last talk about, and when?
I need to know if this is an avid user? Show total read time, total posts with viewed flag set, and total topics entered. If we must display “street cred”, this is a better metric. You don’t want to have a conversation about WW2 with the guy who just skimmed the wikipedia entry, you want to have a conversation about WW2 with the guy who read the entirety of Rise and Fall of the Third Reich.