Per old upstream's https://secure.phabricator.com/T4610 ("I suspect no installs are ever interested in spiders generating an index of Diffusion.") and per current upstream's https://we.phorge.it/robots.txt including Disallow: /diffusion/, I propose to also disallow indexing Diffusion URLs like https://we.phorge.it/rP7868ab3754fad13714640451d664d5bc71b7a02f
This is something that may be not appreciated by some people.
Not everybody likes GitHub and not everybody mirrors things there, so, some public installations may like to have commits indexed on search engines to simplify troubleshooting in general and attract new contributors who are looking for something that is already fixed by a specific commit that has a particular commit message.
Indeed you may say that Phorge already has Differential revisions with that, but any commit does not need to be associated to a Differential revision. So I'm inclined to say that this is not an optimal default.
It should be easy for other installations to do that, but I don't think it's a good default to de-index all commits.