Convey your ideas succintly. It will have a greater impact and more people will read it. Be cautious with humor and sarcasm. Typed language is naturally colder than spoken language, because it is stripped of voice inflections and body language. Quite easily, humor can be taken as insult, especially if subtle.
Some users prefer to use symbols that hint at tone.
E-mail lists are as good, and only as good, as the subscribers make them. Lists work best when intelligent people bring fresh knowledge and ideas to the table. New ideas can stimulate discussion. Trivial or inane comments often kill discussion. Write thoughtful things and everyone will benefit from the list.