*(I'm going to treat this is a non-SE comment question...)*

First of all, a quick note should be added after you clean them up. It might say something like this:

> **Moderator's note: please do not add comments that are not constructive or comments meant to be funny.** If you want to talk about this question use *[other means of communication]* to do so.

After that, you can't do much. Users will do whatever they want, and it is pointless to ban someone for adding a comment. You can't fight this...

Specific to SE, moderators can lock comments to prevent this.