Nice! It's a pretty self-contained patch, so I was able to add it fairly easily. I left a warning on the post page, though, since I don't think it was otherwise obvious enough what was going on.
Thanks @theymos for this quick implementation. I believe it will be useful for everyone, in some moments when we want to quote something from a blocked topic.
Congratulations once again @PowerGlove on your patch being added.
With your worry on this warning is not obvious enough, that I agree with you
Theymos' concern was for the situation without the warning.The current message is indeed not very obvious, but the missing Post button is a good indicator to look further.
What @theymos meant is that this implementation is not obvious and we would all see it soon.
Not everyone would quote a post in a closed topic right away, or do it every day. So without a warning, it would be difficult for most of us to realize that this patch had been added.