>>5,6
Ha-ha @ those who don't understand sage.
There's no such thing as saging a
thread. A sage is applied to
your post, making it not bump the thread. That doesn't mean other posts can't bump the thread thereafter.
The purpose of the sage feature is simple: to use it when you did not post something significant enough to move the entire thread to the top, or when you just do not wish to see the thread bumped (with your own post). The former is actually considered politeness in some textboards (though it's retarded when they try to bitch about it and force you to do it).
The latter doesn't directly "affect" the thread. What does affect the thread (passively) is when people stop replying to it (or everyone who replies sages their post) while other active threads exist - the thread fades away from the first page and sinks below. In imageboards, threads are flushed as they hit the bottom, going 404. But in the textboards, threads are archived indefinitely. So even in the worst case scenario, there's no reason to bitch about people using sage here at all.
tl;dr Stop bitching when someone sages their post, please.