It’s important that people feel comfortable and relatively safe when contributing to a community. A big part of that is setting an example and clear criteria for what is appropriate. This can commonly be achieved by way of a Contributor’s agreement, Code of Conduct, or similar, but in the case of SourceCred, after doing some poking around, I think that SourceCred would do well with something like a social contract, akin to Debian’s https://www.debian.org/social_contract. I think it would be most appropriate on sourcecred.github.io (hence why I originally posted on GitHub) because (when it’s finished) it will be less a “come and discuss this” sort of thing, but rather “this is our finished document” sort of deal. Of course discussion around it can go on here, but I wouldn’t expect a new user to need to search through these pages to find the current document.
I think ideally we would combine the ideas from the landing page (goals, transparency, etc.) with some basic community guidelines about how to treat one another, and what the project can (generally) promise, and what not. It’s the one thing missing when I visit sourcecred.io.