> I've noticed that you RinkyDinks usually reply to a post by leaving what was
> already written and writing under it.

> Yet on other forums I'm on they merely delete the entire last message and type
> away with their own stuff. The whole reason I brought this up is because I want
> to know why you guys write replies this way, and if you always did.

The replies you've had already cover a lot of ground, but here's one more thing to think about:
Sam's forum makes it easy for us to quote messages in replies; when we write a reply we're automatically given a copy of the message we're replying to. Many forums don't do that. If you want to quote from the message you're replying to, you have to type the quote out, or do some complicated copy-paste operation.
On forums like that, people might just decide that it's easier not to quote.

Paul