I don’t understand people who post on the sixth page of a thread and comment purely on the OP. It feels extremely rude. They often ask questions already answered at length, drag the conversation back from where it has naturally gone to, repeat misunderstanding, or just make a contribution that is pointless. Surely if you’re going to invest the time to post at all, you at least read the OP’s posts and the last few comments? Otherwise it comes across as just not caring and not really engaging, not to mention slightly odd to think that no one else might have made your basic point already.
It makes posting on long threads very frustrating to see the same things being said over and over.