Being "nice" is a good goal, but it's pretty abstract.
I don't always do a good job with it in my posting, but what I find generally works when I slow down and practice the following:
1. Posting on the internet is a pretty isolated activity and sometimes it is hard to remember that these are more than just images on a screen. A real person posted them and is sitting on the other side with emotions and feelings.
2. If I have time and am being deliberate about it, I'll read my post out loud and imagine a person is sitting in front of me. When I do that, I find I'm less likely to be rude or flippant and I will edit things to be more kind.
3. If I'm engaging with the ideas and what the post says and not trying to get into a battle of wills or wits with the other poster, I find I do not use the word "you" as much. When people hear the word "you" they then stop hearing what's wrong with a concept and instead it becomes a challenge to them as a person. Limiting the use of the word "you" and instead putting things into the third person to address the ideas, or even better, using the word "I" to describe how a particular concept or argument impacts me, is far less threatening and takes the personal element out of it to where a person will be more likely to agree with what you're saying without losing face or being made to feel stupid or ill informed.
4. Responding to someone elses emotions (or perceived emotions) in kind is usually a red flag to a bull and ensures the conversation will go nowhere.
5. The use of absolute modifiers (i.e. always, every, all, none, never etc.) will usually (see .... I didn't use an absolute
) cause someone to shut down and stop reading what you're saying, especially if you're using the terms emotionally to try and strengthen your point by overstating it. Better to avoid absolutes where the subject matter doesn't truly support them and recognize that exceptions often exist. People will be more likely to listen and less likely to tune out and write you off as extreme or inflexible and be more likely to accept absolute claims from you when that's really what you want to do.
Writing on a Discussion Board too is different that writing academic papers. Try and keep it short. Break up your paragraphs and be as succinct and direct as you can. Watch your tone and realize that people who are already argumentative and being personal in their own writing will see those qualities in your response, even if you don't intend them. Give them less cause to see that by being careful in your own response.
Following my own advice to keep it short, that's all I have to say for now.
blessings,
bart