Hey,
Yeah you do need to enable it, you can do this by logging into your admin panel then navigate to: USERS>> PROFILE DEFAULTS>>Turn on Quick Reply. with regards to editing the text box... Now i know you can edit "for example" the size of the box with CSS but i am not 100% if you can make it persistent across all posts but i would have thought its possible.
What i would say is that if you did do that it may result in the thread layout looking messy and cluttered unless you style it in such a way it fits nicely, "just my opinion"
Hope this helps!
