Thread:Tamer2312/@comment-2234004-20141114131723/@comment-2234004-20141115133518

Well, in most cases, it's just your self-satisfaction, since the discussion is dead (hence why these are called "necro") and people won't respond to it, so your commenting is nothing more then spam; if you need to say something, make a new comment.

Then on the functional side, necros tend to be "stupid" since you're commenting on something that lacked information at the time, so you telling them something you know is moot since they already know that themselves, they just didn't know at the time.