Cassin,
I fully understand your objections. Changing an extensive forum like this needs first of all thorough evaluation of pros and cons since any modification involves re-programming from your side and which means investing time.
And of course, nobody can tell you beforehand whether a suggested rating system will be useless (as you think) or welcomed by most users as I strongly believe ( I outlined various reasons for the why, including benefits for yourself). One thing is for sure: as many arguments we exchange - only if we try it out we will finally find out.
Let me just respond to your last post including your legitimate arguments, to give you final thoughts:
I am sure you have visited the very popular amazon.com. In my view this is an excellent website how a rating system has been implemented successfully:
People can see on the spot the amount of stars based on how many people have given their rating. And this is an ongoing, growing process.
Discouragement of new postings?
Now you argue that people looking at rated postings in this forum might assume that there is nothing to add to them. Now when you imagine eg. a separate column or line on top of a posting saying "current rating"...I can tell you that people are not stupid. We aren't dealing with kids but with adult people who are hungry for information or/and want to pass on their experience. Of course, if you stil feel uncomfortable it's up to you to have information about this feature introduced in your introductory section.
Accuracy of Rating?
Of course regularly it happens that we find more or less "weed amongst the crop" and which results in the rating we give to a posting. So, with a rating of eg. 9.5 I expect to find rather little weed. And that teh stupid stuff will be somehow dealt with - either be ignored, corrected by other contributors or that it simply is so insignificant compared to the rest of the thread's high quality content that it really doesn't matter.
Old Threads?
Referring again to amazon.com it says something like: "this article hasn't been rated yet". And the same could be applied to this forum just by giving every thread a virgin state.
A final thought:
Have you ever thought that a rating system might improve the overall quality of postings?: Who wants to get bad marks?
Anyway, I accept whatever decision you make since you seem to be one of the creators of this forum.