Immature to one is playful to another. :-)

It's all going to depend on the team; it would be a mistake to conflate seriousness with competence.

I personally see it as a filter to exclude those who find things too seriously.

We are all gonna die anyway. The mature commiters too, including everybody they love.

And all of their "serious" work will amount to absolutely nothing in just 100 years (that's it if they're lucky: for most their work wont matter at all in 10 or 20 years, their companies shuw down, or bought and dismantled, their startup dreams shattered etc.).

(A lot of them will even regret working so hard and giving importance to the BS they gave importance to after they retire).

Just to put some mature perspective on being playful.