I am by no means an authority on this subject but I have a few ideas or suggestions I will send your way.
First off, I think you might be slightly confused about the purpose of score. It measures quantity not quality. Any user can gain a significantly high score by creating masses of junk content. So, I would recommend you put that out of your mind as a way to determine the quality of the poster. I have read documentation about the "karma" system, which seems to be more appropriate. You can find documentation about score versus karma. I haven't yet used it myself but this seems like a better (but still not perfect) way to minimize the posting of inappropriate content.
I think it would still be a manual process and you'd have to periodically check the comments that have been posted (can be done on the tiki-list_comments.php page) to view/remove any material.
Second thing, and this may not be a consideration for you or not but you might want to think about using categories to restrict access to certain site objects e.g. particular wiki pages or forums, for which you don't want general members of the public to be able to see or comment on. I've done this on a couple of Tiki sites I operate so that although anonymous users can see certain features e.g. Wiki Pages, if the Wiki pages are placed in a certain category then the anonymous user doesn't even know those Wiki pages exist, let alone comment on them.
I would suggest that you narrow your focus. I know normally looking at the bigger picture is a good thing to do but in the case of Tiki the bigger picture can often be so big that it's overwhelming. Pick a feature and focus on it, like for example the forums, which I feel would be easier than other features to moderate because it allows (AFAIK) for moderating of all posts before they are made public. I've not used the feature myself but this would be the type of staging you are looking for in this specific case of the forums.
You could also consider a completely different approach and not let the general public comment directly on anything at all but have designated place for them to comment on all material. For example have a dedicated forum or guest book (using the tracker feature) to which the general public should direct all comments. This may or may not be an appropriate solution but it is a solution.
I hope I've helped, even just a little bit. Other users may have some more concrete ideas or examples.