I've struggled with this for years and have done a lot of the things you've described, both the bad behaviors and the good suggestions. I still have trouble with it, especially over the Internet.

I'd like to point out that, at least in my experience, it takes a lot of practice to avoid offending others without offending your sense of self. I've also found it much easier in person, where I can use tone and a natural lack of seriousness to paper over any rough edges.