I think humour in a roleplaying game is super important, pretty much no matter what you’re playing.
In a serious game, a little humour – preferably set within the game, rather than breaking immersion – is a way to release any built-up tension, so that you can start to build more. There’s an upper limit to the tension you can build at any table.
The best sessions I have ever played or run have been a combination of humour and tension. The balance doesn’t always work out, and that can mean that the game falls too far in one direction or the other.
Consider the balance when constructing your session, and give the players something that will allow them to let off steam… even if it’s a guy with a wheelbarrow who sells vegetables and has a sense of humour in the post-apocalypse!
It would be remiss of me to end this post without mentioning Era: Lyres, which has facilitated some of the most humorous games I’ve ever played – the night in the mansion with S’coo’b’y-d’oo and the group’s evil twins who all are the same but have moustaches is, reluctantly, a high point…!