Seems like I have to learn japanese ;-)

Have you already thought about a quote-function for each post? So that in the head or at the bottom of each post will be a quote-button which starts a reply with the whole text of the post as a quote. The quote-tag could be like the following:

[quote="username"]Username wrote: The quoted text[/quote]

Username has to be replaced with the username of the author from the post from which is quoted.

This function is implemented in phpBB2 and I find it quite usefull.

..::Edit::..
Ah, forget it. I have just seen that you already inserted that function at the end of the reply-form.