It should respect the forced flag in MKV. And I just tried, and it does here. Subtitle Mode is "Do not show subtitles", default languages both English, and the forced track was selected by default on playback.
Edit:
There was one limitation in there, namely it required you to have languages properly set and those languages to match. So instead MC will now always select the first forced track if none was found with a proper language choice.
For the best results, always configure default audio/subtitle languages in MC.
Hendrick, on start of the movie default/forced subtitles are usually selected. Try to manually set subtitles to "OFF" in menu while movie is playing. Unless its a PGS subtitles with properly set PGS internal force flags, there will be no subtitle shown even if MKV marked them as forced.
I just tried it on MKV where I deliberately set SRT subtitle to force and default in MKV. On start playing SRT was selected, but on choosing "OFF" subtitles disappear.
Same happens with PGS subtitles with PGS internal force flags known to be not forced (I just remux one of my MKV and set normal PGS subtitle stream to be marked force and default in MKV)
On start playing PGS was selected, but on choosing "OFF" subtitles disappear.
In my experience only PGS subtitles with properly set PGS internal force flags will show when "OFF" option is chosen.
I explained in my previous post how to set internal force flags in PGS. There are some notorious BD that have force PGS subtitles with internal force flags not set (Captain America Civil War 3D, Last Samurai, Black Panther 3D ... to name few i came across)