Nobody wants to make more work for you, Lester - but if the opportunity arises... I find this annoying too and have been caught by it more than once. Don't think of it as a fix, but rather a usability enhancement.

For me, the similarity in the titles is the issue, given "Post Quick Reply" and "Reply to Thread" are very similar, and "Reply to thread" is bigger and high contrast, it's an effort to not click it.
Would it be the same pain (or would it help) to change the text on "Post Quick Reply" to simply "Submit"?

A minor issue, not high priority, but I'm betting there are a lot more folks have done it than just us three.