I'm sorry, but I don't see the quick reply button as a feature that'll bring death and destruction to the forum. If phpBB 2 isn't broken, why is it a concern to upgrade it? Because it'll improve the forum, in a similar way that the quick reply button would. It's not like anyone is demanding a massive change, simply a feature that would be enjoyed by some users. Some may not, and by all means, they're free to disable it. While some users want such a feature though, I do not see why it should be prohibited. I'm even sure some people would change their minds after becoming acquainted to it!
Click the wonderful signature. You know you want to.