I have seen that many people still post a separate "thank you" instead of just clicking on the "like"-button. How about adding that to the Posting Guidelines?
That might help. But sometimes I get the feeling that the Posting Guidelines are a bit like Operation/Instruction Manuals: everyone gets to see them, but few actually read them.
Maybe making the 'like' button more visible would help: either somewhat larger, or in a brighter color, or placing it to the left of the screen...
Please be aware that I'm neither a native English speaker nor a teacher.