After having thought about this for some time, here's my take on the like button:
Like buttons are usually used on "amateur" sites like Facebook, Instagram, etc where you usually communicate with people who are actual friends and family of yours. In that amateur setting, it feels good to get a "like" when you post a picture of your cat, grandchild, or home-made pizza.
But in more "professional" forums where you go to get advice from "experts" from all around the world -- people that you mostly have never met in the flesh -- a like button is superflous and may even cheapen the experience. I cannot remember having seen any such button in any other "professional" forum.
If Flyertalk had adopted a "helpful" button with the possibility of e.g. sorting posts according to "the top 10 most helpful posts of Trans American Airline forum during September 2017," that would be another story. That could actually be a really good addition to the site. But type of "dumb" like button serves no practical purpose at all, so it feels kind of misplaced. You're left wondering what this elephant is doing in this tiny room?