First of all, it's not too complicated to subscribe to the list. It takes a few minutes to sign up. It takes less time to sign up than it took you to write this email.
I signed up myself fairly recently, and it was also for a "single use". And then I never bothered to unsubscribe. But that's also simple.
Unfortunately, gmail by default uses "repy" instead of "reply-all", so I almost hit send before I noticed that I hadn't replied to you.
To save you a few minutes, I've taken the liberty beginning the subscription process for you.
This is in some sense a bit rude and presumptuous of me, so if this not what you want I hope you'll forgive me.
Anyway, about your actual question...
I think this is a very old feature, and I've used copy and paste through PuTTY before, so I have no idea what's going wrong for you.
Here's a quick-and-dirty workaround. Let's say your shell prompt is a dollar sign, and the file you want to change is config.txt.
Then do this:
$ cat > temp.txt
PASTE YOUR LINES HERE, USING PUTTY
NOW PRESS CTRL-D FOR END-OF-INPUT
$ nano temp.txt config.txt
Now you can use copy and paste within nano itself. After you're done, delete the temporary file.
Hope this helps.