Can a girl and a guy just be friends?

I apologize if my comments were taken as an offense by sister, but my intentions were only to share the truth how I sincerely feel about it. If my way of conveying was wrong, I regret it and inshaAllah would be more careful in future. I am not on GS to make female friends. That is why I use the word "Sister" in my comments as all the female members on this forum are like my own sister except my wife.

I have discussed the matter with few scholars because I myself was very confused on this subject (sharing views on an online forum with both genders) and how does Islam address this Issue. I even left forums for sometime to first clear my understanding on this issue.

The reply I got was that Quran call muslim brothers and sisters as each other's helpers, and there is no problem in sharing good knowledge for everyone to read, as long as one is not exceeding boundaries. (avoiding personal chit chat (by the grace and mercy of Allah (s.w.t)

If anyone kindly show me a hadith or Quranic verse that proves that one can not share knowledge on an online forum with mixed genders, I would inshaAllah try my best to never return to this forum.

May Allah (s.w.t) guide us all towards the right path. Amen.