I'll pose it here, even though it's not really specific to the front-end. I can just disable it once the media is playing if I play it directly in Media Player Classic outside of the interface. It's specific to the MPC program itself.
I'm using the CCCP codec pack, I can get any file I want essentially to play back, but the .mkv's I've made and have use the dang english subtitles at the start.
Does anyone know the registry entry necessary (or setting that I'm missing) to disable this in MKV files with english subtitles recorded in the container?