We had a thread about BST etiquette about a month ago. Some people took offense. (Go figure, right?)
You are 100% correct. I suspect that most offenders do not understand the difference between an edit and a new post in the thread. They don't realize the subtle difference that results in a bump.
My pet peeve is the SmokeyBurgess type, who constantly list things and then deletes them leaving lots of blank messages. But that's just me.
Edited to show the thread:
http://www.net54baseball.com/showthread.php?t=121294