a visual quote editor
 

I find a lot of brand new users to my forums still have a hard time not breaking the [quote ] tags and leaving stray quote] tags around. It might be nice to have a more visual quote option within the quick reply / post reply. It might be handy to even prompt new users if an unclosed/duplicate/mangled quote tag is spotted.

I suppose this is probably way overkill* but I find myself fixing bad quote tagging a good deal with new users.