As someone who has participated here for about 9 years and H20 for about 5 years before that and Associated Jehovah's Witnesses for Reform and some of the news groups even before that, I certainly agree with you that conversational tone was different 10 years ago. Discussion boards morph and change over time.
More has changed than just the tone though. There is a document on logical fallacies on the internet that opens like this:
"There is a lot of debate on the net. Unfortunately, much of it is of very low quality. The aim of this document is to explain the basics of logical reasoning, and hopefully improve the overall quality of debate."
Quality discussion requires some basics from both sides:
1. Understand when a conclusion follows from one or more premises and when it does not. Logical fallacies are not a matter of perception.
2. Know your subject extremely well.
3. Try to know a little bit about the person you're talking to as well. Do they have qualifications in this area? If so, what are they?
4. Understand the opposing position. A cardinal rule of debate is that you must understand your opponent's position so well that you could argue it for them.
5. Above all else, be honest. Both sides can make valid points in a discussion. When someone positively demonstrates via hard evidence (Mathematics, Authortative sources, etc.) that something is so, acknowledge it.
The example I gave (i.e. 'Friend') had some very long and very spirited debates with Alan Feuerbacher, "Farkal", and several others including myself. Not everyone agreed with him, but he gained a great deal of respect because he understood these basics very well.