I have had my fair share of that experience and I can attest to it that it took a lot out of me, not for the time spent in making the post but on realising I was spending all that mental energy on a locked topic. Loll.
Have you ever just finished writing a reply to a post in a thread on bitcointalk and tried to publish it, only to discover that the thread had just been closed? Even though you'd recently managed to click the "quote" button, meaning the thread was open
You can quote locked topics as well. It's been that way for a while. It think it was implemented by PowerGlove.
It is for this that you can well have quote on locked topics that make sure to watch for the reply before checking for quote. Locked topics do not have reply button active.