Thank you so much for your explanation.
Your point reminds me of the ironic use of some words I heard on TV when I was watching films. For example, when people use words such as "interesting", "lovely" etc. I could see the speakers didn't mean what they were saying from the expressions on people's facial expression but I didn't know I can judge it from the intonation. Now I have learned a way to see what a speaker means. However, since the native speakers sometimes fail to interpret ironic statements my chances of interpreting them would be small. Anyhow I'll try.