Say something positive about the person who posted before you and something bad about the person who posts after you. You can make up creative compliments/insults, but make sure none are against forum rules.
Also make sure the insults are actual insults and the compliments are actual compliments. Saying "you are a banana" could be a compliment or an insult depending on how you look at it. So don't say something like that.

The idea is every person should get insulted by the person before them, but they must say something nice back. Preferably compliments should be specific to the individual to make it more valuable.

I'll start:
The person in front of me is not here, but I know he/she is very wise for not wasting time on the forums.
The person after me has a face so ugly, even blind people turn their heads away when walking by.