Snap responses often lack clarity and depth and can be inflammatory. Keep your posts civilized. Many lists have moderators to keep the participants in line, others are unmoderated and require maturity on the part of the participants. Only include the pertinent portions of a message when replying to posts. Excessively long quotes, unless needed, just waste space.
Flame mail is derisive and inflammatory, typically little more than name calling.
If you must respond to a negative post do it directly don't waste bandwidth on personal replies. Don't post off topic information to the list. If you are on a list that discusses Rose Gardening a post about NBA playoff standings would be inappropriate. List Warning Lists often have very high volume traffic. It is advisable to setup a mail filter to file the list mail to a folder for easy separation and access.