Hi there,
Currently, that how it is actually. It will always take current menu items as you created another menu items for your 'my post' sections.
It is advisable for you to use 'Use Menu ItemId Determined By EasyDiscuss' as it will always refer to 'Easydiscuss Frontpage' menu items, that is used to route through-out the site.
If you wanted to use ' Use Current Active Menu ItemId ( default ) ' you need to re-assign your menu items accordingly so that it will always follow it main menu accordingly.
Thanks for your understanding.