Total Karma of a user can be seen on his profile page. Afaik there is no way to see another users average karma, unless he is on the leaderboard, which uses total karma as the ranking metric.
http://news.ycombinator.com/item?id=1741408
http://news.ycombinator.com/item?id=1485254
http://news.ycombinator.com/item?id=1349459
http://news.ycombinator.com/item?id=1349455
Those are all comments by me that were helpful to the parent, but which are "punished" by the public display of avg.
If you want it scaled to fit a continuum of "bigger is always implicitly better", a more reasonable number would be: average of (comment points/parent points)
Even if a number has no [absolute cardinal, > x] meaning, there is still a nominal information value to the datum.
This could help with another gripe I have with displaying average points (and comment voting in general), which is that oftentimes quality comments are downvoted simply for being contrary to the downvoter(s) views, and/or groupthink.