I think this is probably the right repository to open this feature request on.
With github, you can add a .patch to any commit URL and get a patch file.
That is really neat for package maintainers if they want to fetch a patch to be
applied to a package, for example when a bugfix should be applied to a package
in a distribution but upstream did not yet release a version that includes that
bugfix.
It would be nice to have something similar (equal?) for the radicle web interfaces.
(Full disclosure: I am mainly speaking as a nixpkgs package maintainer, but I assume this is also true for other distributions).
Fyi, in nixpkgs we already have fetchRadiclePatch, but this currently only works for whole patch revisions (not individual commits). So, support for .patch urls in radicle-httpd would still be nice to have.