PKing is definitely a skill. The only way of telling on Classic however is actually watching someone PK. If they ever showed deaths in the profile, then you would be able to see who is really good, barring those that lame kills or do some sort of "shifty business" to get it. PKing is almost a lost art imo, a lot of people care more about sparring. I would love to see a server hosted Guildwar, first to 10000k kills gets a hat. Would be fun, would also encourage pking guild, and therefore more PKing in order to practice for it.