SSK above has got it pretty much right. To quote someone, including their PPRuNe name, etc :
1. Click "Reply" in their original post.
2. When it comes back with a blank screen and a url in the address line at the top of the screen ending Noquote=1, just click at the end of the line and backspace over the digit 1. You don't need to replace it with 0 or anything, just leave the line ending Noquote=
3. Press return.
This then does what the "Reply" icon used to do on PPRuNe up to about a year ago when it got changed.