Account selling undermines our Merit system as well because Account selling is similar to buying Merit. Buying Merit is not allowed, too.
Merit sources aren't allowed to sell Merit. Other than that, it's allowed to buy Merit, and probably because of the same reason why account sales are allowed: it can't be stopped anyway.
If we wake up one day to find out that Yahoo62278, LoyceV or Royse777's accounts were bought, are we going to disregard all of their positive contributions and the current people behind these accounts and start tagging them to ruin them just because they were bought?
I can help you here: I created this account by myself. If it ever changes owner, I
expect it to be tagged instantly! It shouldn't be too hard to notice when someone else is posting on my account.
Always stay vigilant.
The most dangerous part is, who are these people to constantly policing over everyone? Ban the signature feature, 95 or even more out of 100 of them will make one or two posts in a month or week. No offense for any specific signature campaign member from Chipmixer, those who used to make over 50 posts per week when Chipmixer was paying for up to 50 posts, how many of them now makes 50 posts?
Take a look at
Active users and top posters on Bitcointalk.org in the past 7 days.
Be careful drawing conclusions from this: it looks like you have many local boards on ignore, which means you don't see all of his (first) posts.
Why should members here continue to write quality posts if you can buy Merits and get accepted into the best paying campaign and also stay in it for shitposting one-liners 24/7??
Allow me to quote theymos on Merit sales:
Merit sales, transfers to aliases, back-and-forth trading, etc. are not much of an issue. All illegitimate merit will decay, and will account for a tiny and very expensive fraction of the total merit economy. It's basically a rounding error; fight it where convenient, but waste no sleep over it.
The real problem is campaigns paying shitposters, see the above 7 days link: massive spam paid almost exclusively by the same signature campaign.