Do you realize that there are already people with existing cookies from perlmonks.org?
Uhm... so....? We're not using this solution because everybody with a cookie on perlmonks.org would have to login once
The device has yet to be invented that could notice that miniscule of a difference in server load.
There is the redirect solution. It doesn't cost anything and would work also for links posted somewhere else.
There is the explicit-domain-cookie-solution. It doesn't cost very much cpu (just check the server host and decide which cookie domain); it only needs some code (I can't estimate since I don't know the existing code).
It also works for links posted somewhere else.
Still you favor the solution which costs the most cpu (and probably the most coding) and which only works for links posted on this site, because you think the load is not measurable? That's kindof like saying, as a european (or american, ...) I still want to drive my big car because it's of no use to save gas, there are much more cars in china, so if they
don't save gas, I shouldn't either.