Selection subtitle extension

I don't exactly if this is the place for this, i'm sorry if doesn't (my apologyze for my poor english too)

I think it was a very useful improvement if the users could choose the subtitles file extensions to download as well we can choose the language/s. Because the first option may be .txt and matroska edit tool don't recognize this extension to integrate subtitle into the video if users want to do this.
Thank you very much.