Since you brought this up..........i've never in all my years buying and selling pool related items seen anyone trying to sell a USED TIP! You are also correct that that thread is taking up valuable real estate in the Wanted/For Sale section.
I don't think it's against any rule, but since i'm posting in this thread there's a seller who has "10" for sale threads on the first page at the same time! How inconsiderate is this guy to bump all his threads to the front page at the same time and move 10 sellers off the front page. I'll refrain from mentioning who it is, but he's taking advantage of the forum's free Wanted/For Sale section. The least he could have done is bump a couple of them at a time if he has that many for sale threads going at the same time, but by bumping them all at the same time he's dominating the front page.