Following on from the editor fix, the public recording player (/r/{uuid}) also used a fixed 16:9 box regardless of the recording's actual shape. It now reads the video's real dimensions once they're known and sizes the player to match, the same way the editor does - a portrait recording gets a portrait player instead of a landscape one with the video shrunk down the middle.
Shared recordings now play at their own aspect ratio
Watching a shared portrait (9:16) recording pillarboxed it into a fixed 16:9 landscape player, leaving it small.