“like” and “comment” are two very different things.
Comments: yes, commenting should be built into almost every single theme for WordPress. It’s difficult to find a theme that doesn’t have commenting allowed.
You also need to make sure you have it enabled under Settings > Discussion
Likes: you could certainly add the Facebook like button to your posts, but there’s no “like” engine within WordPress. WordPress (.org) sites don’t have their own social graph by nature, unless you run a BuddyPress site where people are registering and friending each other, so there’s no way to really add a “like” button without having some sort of social graph to start with.
