Ok. Time for some dumb questions.
How does this work, if the project has direct payment active.
Who has control over the revenue split ratio.
What happens if one of the enthusiasts doing revenue split on their hobby project screws up tax information or gets legally, because their business partner did not uphold agreements in shared work.
Who can remove the project or change the price.
To my limited understanding a thing like revenue sharing is not possible at this point of the chain of distribution. You need to have a single entity having the rights to sell. A single entity responsible for all the legal stuff, including holding the rights of the project. After all, the project could be sold on a different platform and different distribution channels as well. If you "share" on itch and your partner sells it on their own website without sharing, how to deal with that.
If you do a limited colab to bundle sell things, that is different. There are two entities having each a concrete project and agree on a limited sale with a defined sharing option. The purchase gain is shared, but the projects are still separate and can be separatly be dealt with legally.
In reality of course those entities are small companies that are still often controlled by a single person, but the legalities how the company is controlled is the internal affair of said company. Trying to do revenue sharing on the distribution level of the sales platform is making those internal affairs external, actually making the company obsolete.
That is my two cents, and I know very little about all this stuff, but I believe there are loads and heaps of pitfalls, that people naively do not consider when idealistically thinking about revenue sharing of their hobby projects. Sure, it sounds fantastic, some strangers collabing on a project, making money along the way and sharing the revenue. But I fear itch has not the legal capacity to be such a place.