Post Ranking, programming?

Hi everybody;

bite me if this does not belong in her, but as i have some questions linked together, i did not know where to put it else.

My general interest is that i would like to add a possibility to a forum for registered users to "rank" posts, e.g. like Amazon does this with user comments. The idea behind this is to motivate users each other to write "good" posts. I asked about this in "Modifcations" but received no reply. Can it be true that no one came up with  a similar idea yet?

If not, well i have a follow-up question. Although i do not consider myself a good PHP coder, i would the try to build something like this myself, e.g. in form of a modification or some sort of board extension. What i am a little bit afraid of is that PunBB 1.3 was originally announced for last year, and may just be arriving while i am developing. I simply would not like to build something for 1.2.X and then have to rebuild it immediately for 1.3 just to keep pace.

If there is no such extension yet and i consider digging into this for myself, does anyone have input on how "compatible" plugins for 1.2.X might be for 1.3?

Thanks in advance for your answers.