I think that (at least in terms of pointing out trolls or great forumers) this was intended to help those newer to the forums who may be fooled easily by trolls, or just don't know which forumers are....less trolly I guess. Right now it seems that a fair few of the fresh spawns check the post count and base their assumptions off that (eg, a fresh spawn sees a forumer with 5k posts and assumes they must be great forumers). The rep system could (potentially) change that to the fresh spawn checking the rep of a forumer and basing their assumptions off that.
Hopefully that makes sense, sorry if it doesn't.

