My feel is that the icon is too bloody big and garish. Does it change to something else when someone has liked a post?
We tried a lot of different icons, wouldn't be difficult to make it smaller, but it has to be large enough to be clear on phones. When you like a post, it changes color, if you click it again, you unlike the post. There are permissions options that can be used to limit who sees what about their own and other users' likes.
If it is worth a thumbs up it is worth a comment period
You should be able to have a different CSS style sheet for different devices or resolutions. I'm not sure how easily that can be configured on top of an "out of the box" forum software though.