Manuel,
That's normal behavior. Just clicking the Like button is not given a lot of prominence by Facebook anymore. Adding a comment to the Like is a way for the user to tell Facebook that the Like is important and that they really "Like" the page.
To verify that the Like actually went to Facebook, you can click the "Activity Log" button under your cover photo on Facebook. You should see the Like action in that log. You can also click the circle icon and force the Like to show on your Timeline. The default is "Can show on Timeline", in which case Facebook determines if it will show.. and, without a comment, there's less of a chance of that.
I hope that helps explain,
Alex
"Likes" are not published on user's wall [solved]
