Most Helpful Girl
Don't do it. If you are trying to get a reaction from her or drop a hint you're into her then message her privately. Otherwise leave it be.
Most Helpful Guy
If you are struggling whether it's okay to do it or not, when it comes to Facebook - DON'T. Your comment won't do much anyway, only do it if you are 100% sure you are okay with it. And I already know that you are not.