There is now a global jit USE flag with the following description: "Enable just-in-time compilation for improved performance. May prevent use of some PaX memory protection features in Gentoo Hardened." If the package's local jit USE flag description does not offer valuable information beyond the global description, consider removing the local flag from metadata.xml.
I'm not sure about that. The flag desc says SSE2 is required; I'll probably should add some kind of check for that (+ewarn) in the ebuild...