Hi Wull,
I requested the change because the filetype .mkv and .mk3d were grouped. This meant JRiver would attempt to play my 3D MVC encoded mkv files which have the filetype .mk3d.
Since Matt made the change (thanks again) JRiver plays all my MKV files but any 3D files are handled using StereoScopic Player which supports true full resolution (via HDMI 1.4) 3D. When I press stop on my remote (which is mapped using LCDwriter) then it passes the command to StereoScopic Player to quit rather than stop and this passes me back to JRiver.
I do all my 3D ripping to 3D MKV using MakeMKV and tick the option MVC in the data stream.
John