Such examples would be in the extreme edges of the bell curve though, and rules designed to suit those rarities are often not suitable for the people in the main part of the curve.

And even so, a single commentor that only has 3 comments might make valuable comments when they pipe up, but the 2000-commentor is more a part of the community simply for having more frequent conversations.

You say you have a low average and therefore aren't as valuable a community member, but I recognise your handle and have a general idea of the flavour of your previous comments. In business parlance, you have 'brand recognition' :). If some wunderkind blows in tomorrow and posts a couple of popular posts (popular gets the votes, not insightfulness) and afterwards departs or lurks forever, I'm not going to remember them or their 'flavour', despite the high average. They might have made an interesting observation, but they wouldn't be as strong a part of the community as yourself.

Besides, getting back to context, who would I trust more when it comes to this 'endorsement' process, silly as it is? Someone who breezes in and out and mostly lurks, or someone for whom talking on the site is a frequent occurence and who knows the ins-and-outs of it? A lurker is an unknown quantity, but for someone to hit [number] karma, they generally have to have chatted or posted a bit (a few exceptions, sure).