I actually just removed the item entirely (here's what it used to say: "200 with Location: header for synonyms. If an object is available at more than one URL, operations on the secondary URL should return the object’s value with a Location: header to identify the primary URL. Most clients won’t be expecting 3xx redirects, so use 200 OK instead.").
We don't have any synonyms so far in the user stories for the Core REST API. I think the most likely situation would be with pages; having "/page/{id}/by-id
" or something similar for getting a page by numeric ID.
On the client side, dealing with redirects sucks. You have to put a lot of extra code in to check if you got a redirect back, and then handle those cases. Just returning the content, with a header that tells intermediaries what the best URL to use is, is more developer-friendly.
I definitely understand the cache-friendliness question, though.