I noticed that downvote buttons disappear after a while (24 hours after posting is my non-scientific impression), but upvote buttons never do; If e.g. 95% of the votes happen within 48 hours of posting, it might make sense to drop the upvote buttons as well at that point, and display the points -- if you believe they are useful.
Personally, I'm happy with the comments just sorted by points and don't care for the actual number -- although, while you're at it, I would be happy if there was a controversy indicator of some sort -- when I read threads, I'm often interested in the consensus and the controversial. I can find the consensus in the first few posts; I can't tell where the controversy is.
I mostly see this in the form of low quality or offensive comments that get lots of up-votes from people who agree with the poster's opinion - usually if a good comment gets down-voted because the majority disagrees, someone says "why the down-votes? its' a legitimate point", and it gets boosted back to positive.
Having the comment scores show up after some fixed amount of time (1 month?), would add a little to that experience.
I think they would, could... ok, might have more value, if there was some way to get them more easily in front of the right eyeballs at the right time. How many "seeking advice..." threads appear that remind us old timers of one or several prior discussions that would still be highly relevant.
If we have the time and inclination, we google or otherwise search up a link or three. When someone else does so, I know that I for one am inclined to follow those links.
Seeing comment scores is useful, because it lets me easily see the "best" comments. I don't see the problem with showing comment scores once the discussion has died down.
It's also useful to be able to see comment scores when browsing old threads, looking for specific information (using searchyc, bookmarked threads...).
*: of course, this approach is good for simple HN "consumption", but participating is harder, since few people reads the comment I make on week-old threads...
This is actually why I think comment scores should remain off indefinitely. People (including myself) have become too reliant on scoring as a measurement for the merit of comments. That may have worked when the site first started and had a small close-knit group of users. However, any site which experiences growth as HN has will inevitably become diluted for both quality of comments, and scoring, I believe. Yet, people will not adjust for that as they continue using scoring to inform them what is "best".
In other words, when I use HN on a daily basis for the community, I'm browsing the latest articles in high-volume fashion. When I use it as a technical resource, I'm probably only hitting a few old articles. But pageview-for-pageview, the old articles that pop up when I'm doing a search offer me much more value than the ones I browse daily.
While you must certainly be right re: the degree to which traffic goes to old vs new articles, I think you might be underestimating the value of old HN threads. The traffic going to old articles probably has different purpose and those pageviews are probably not isomorphic to typical pageviews coming from the front page.
Judging from the replies to your comment, pg, at least some people read old threads. I know I do. I find helpful advice and information from them all the time. I think that people reading these threads should be able to get the benefit of seeing the scores.
The arguments against showing comment scores are almost exclusively about the thread quality. If the scores aren't shown until it's too late to comment, there isn't going to be any noticeable impact.
If I haven't overlooked anything significant here, you wouldn't be hurting any aspect of the site, but you'd be helping some people get more out of it.