A question came up in today's session: what metahuman languages, if any, do spirits speak? I don't know of any clarifying passage in the book, so my off-the-cuff ruling is that a spirit has the same language skills as its summoner (in this case, Norwegian N and English 4.) Does RAW address this issue at all?

To my knowledge no and it's always bugged me, though it has yet to be an issue in my game. I don't really like the idea of spirits being limited by language - traditions encompass many languages so how would it be that a summoned spirit always knew the right language(s) and never the wrong ones? I'm tempted to house-rule it that spirits communicate psychically. Can anybody suggest why this might be a terrible idea (as I suspect it might).

It's RAW that spirits have a psychic link with their summoner, but I'm not wild about the idea of general telepathy. That's just me, though.

We don't even know what senses they have, besides Astral Sense. I'm not sure spirits can hear or speak, let alone in the right language(s).