IE has full support for Unicode Bangla, and so does the FireFox. If you want simple step by step instruction to enable Bangla in your computer follow this guide:
http://www.banglacricket.com/tools/bangla.
Unicode Bangla is platform independent, operating system independent. It works in Linux, Windows, IE, FireFox, Microsoft Office Apps, OpenOffice Apps; anything and everything that supports Unicode standard.
There is no reason for not using Bangla in forum. We have implemented complete Bangla support in our BanglaCricket Forums since last month.
Avro is excellent software for unicode Bangla interface. Even though there are other unicode Bangla solutions, such as Ekushey and Microsoft IME; I think Avro is the best with its UniBijoy and phonetic typing support.
If we do not use unicode Bangla and keep living in the Banglish world then it will be to our own detriment.