They can't deal with the logic or the message so they distract off the subject and make the presentation the focus to discredit
Well sometimes, if it's the same message over and over over again, others either lose interest completely or have to resort to parsing grammer or playing word games to try to make things interesting. This can be compounded by the fact that there are only so many ways to keep saying the same thing over and over and over, so the original poster has to resort to same. This type of behavior on the part of the original poster is sometimes intentional, with the intent of disrupting a board through passive/aggressive methods. And sometimes the original poster just likes to hear himself/herself type.
Just saying it happens sometimes on some boards. Don't have any examples handy.