I would generally not do such a thing unless I wanted to put such a motion to bed, so to speak. We've voted to table a motion in the past and that's one way of saying, "we've discussed it, we're not interested, let's move on."
Seconding a motion that I am going to vote no on is another way of saying "we acknowledge that some people support such a motion but it is not in the best interest of FlyerTalk."
Either way, it would and has been a pretty rare event for me to motion or second a piece of legislation I will be voting no on.