Because once you have federation you can either use an operator/domain web-of-trust, or you can use allow/denylists on your instance. That's how email or XMPP is kept mostly spam-free (on a selfhosted server most spam - if not all - i receive is from gmail addresses, not from selfhosted servers who are easily denylisted if they start sending spam).
In particular, if an instance or specific repository concerns only people from specific projects/instances, it would be easy to allowlist those specific instances and not have to deal with spam at all.
> on a selfhosted server most spam - if not all - i receive is from gmail addresses, not from selfhosted servers who are easily denylisted if they start sending spam
And most - if not all - potential GSoC contributors are from gmail addresses. So again, I don't understand how this could be a general solution to spam.
I think you don't get my point. I'm not advocating for denylisting gmail.com because it produces spam (although this has tempted me on more than one occasion), i'm saying fighting spam in federated environments has decades of experience of various techniques that work well. Open nodes (eg. remailers) have terrible reputation and are denylisted pretty much everywhere, but specific communities/servers can maintain a decent reputation as long as they have some form of moderation/cooptation. By opting into the federation, Gitlab could support various advanced workflows depending on your threat model:
- a new organization using your project? maybe grant their whole gitlab instance "issues" read/write access to the project
- publishing FLOSS in a "community" setting where random people submitting contribution is not expected? maybe we can check the PGP WoT before deciding whether to accept that PR
- running a federation of organizations, some of whom may run their own instance? allowlist all the instances so they can interact across instances
- running a public forge like gitlab.com, codeberg.org, or chapril.org? maybe maintain an allowlist of servers who ask for it and pledge to fight spam
- feel adventurous? setup an entirely public instance and help catch spam and reporting it to denylists
All this is already possible on email level, but pointless as you pointed out as trustworthiness of the mail server is not correlated to trustworthiness of the forge.
