I know that there is already a different mouse hover effect but I always mistake these ads for links inserted by users. Could you please change the color or the text-decoration property, please?
It's been toyed with before, and where it is now (different hover) was the middle ground where it ended up. You have people that want it all the way one way and others that want it all the way the other... so that was the middle ground.
Okay. If you happen to change your mind about this, this is the way how I'd make it if it was up to me. (BTW there is a book about monetizing forums and it strongly recommends making paid links different than natural links - it makes both users and advertisers more happy because all clicks on ads are intentional and not accidental.)