I noticed your a newbie Urdam. It's an easy trap to fall into - you read 100 posts with many thoughts and opinions, and you see something that you agree with and say so. But we don't know which post you were reading. It's more frustrating though if you write 4 or 5 thoughts and someone replies "that's interesting, what makes you say that" and you don't know which thought interested them, much more difficult to reply.
Rather than click "Post Reply", click "Quote" and the message where you clicked Quote will be included (like I quoted yours above).
I'm pretty sure he was agreeing with Dave00's post right before his? Although it is a good idea to quote the post, or at least a portion of it, that you agree with just in case someone sneaks in a post just before.