Haha, that's funny
You use 'haha, that's funny' on Discord when your friend's joke was so bad it made you want to cry, but you don't want to be a meanie.
'Haha, that's funny' when my friend sent a joke that was just 'I like pizza' and that's it.
'Haha, that's funny' when my friend sent a meme of a cat that looked like it was dying.
'Haha, that's funny' when my friend told a joke about socks and it went on for five minutes.