When you click on that "Like Post", it responds with, "Are you certain?", and if you click "Yes", it says, "Right, come back to me when you've made your decision~" dX ...in seriousness, I don't know, I would say the staff had something to do with it, but there are no staff here at this moment in time (unless they did something last night, and it's taken a while to come into effect).
Just tried opening a new tab with it, and the message shows up. It doesn't when you click it normally, so I'd guess it's your browser settings.
Being in the trash wouldn't be an issue either, as you can't do anything to the posts in the Trash, and that includes liking.
As it was already suggested, it depends on your browser settings. If you can like a post "on the fly", then it won't ask anything. If you open the link in a new tab, or if you disable javascript, then it will ask that question.