Actually, by trying to become "Just friends" in this world, they are becoming enemies of each others in the life hereafter (and in this life as well). Only if they know what "fruits" would that "Just friendship" give in this life and in the life hereafter. They may have Just friendship, only if they are able to find a place where Allah (s.w.t) can't see them.
It is more dangerous to become a friend of na-mehram than to become an enemy. But the enmity should only be limited to avoiding frankly talking,** keeping gaze low*, **avoiding meeting and avoiding sharing personal and family problems*....etc. It would help in saving a lot of expenses and time.
OK, I am confused. I knew this point would be raised from my post. Actually I meant to say that sharing family problems in real life after becoming close friends, which strengthens the bond, gives rise to emotional feelings and leads to further problems in daily life.<---This is not good.
Of course on forums there is no chances of any such emotional feelings or strengthening of bond as the personal information is as limited as possible and only knowledge is shared with all the people without too much focus on any specific persons gender, age, other personal information...etc.