Where does Islam teach seclusion to that extent? Thats quite extreme, because the Men and Women would pray in the same Room i n the Masjid at the time of the Prophet

, Aisha (R.A) Mother of the Believers would teach men from behind a screen etc. Various Scholars had female teachers, and women studied with male teachers. Sometimes it is necessity to talk to the opposite sex in the market or outside. To say this is not allowed (i.e. haram) would mean that if someone did do it are commiting a sin. So, it is not haram or not allowed. There is nothing wrong with using a forum such as this.
Of course, this doesnt mean that unrelated men and women sit together or alone. Or that they speak in inappropriate manner.
Wasalamu Alaykum.