Seems like you're having no trouble with it
It was fine for days then I see "Link Removed" in my signature.
Try making a link to a pools "post" here in the forums... That is usually "tolerated" as it is an "internal link", and cant be used to "direct people to malware". (Not that your link did that... but you don't control what that website places on its pages.)
I am sure it was a general protection. (Should also make you wonder... why DID they remove it. Is that pool legitimate? Do they have issues with that pool? Is it a malware-infected ad-site?)
Also, if you SPAM, and direct people to your signature... they shun on that.