I think this would be a great addition to the forum and eliminate the need for 'this' and [2] posts. There does not need to be a dislike button if needs be so it can be a positive addition to the forum rather than a tool for brigading like past fears which iirc was reason for not having this added.
If there is a need for finding codes for VBulletin to have this added I have done a little bit of research and found these, i'm unsure if they will be any help but they're good to keep in mind.
https://likebtn.com/en/vbulletin-like-button
http://www.vbulletin.org/forum/showthread.php?t=243510
I hope you will have an open mind and see the benefits this could have
