Could there be some other issue going on as well? I just replied to a thread I had "quoted" - my cursor kept jumping up about 3 lines, it would not let me continue typing at the end of my sentence. I haven't had any other PC issues, so that seemed very odd. I finally wrote my reply in a text editor and then copied and pasted to the thread. It is working well now as I type this reply, but did not use the quote feature.
The signature issue was a software upgrade a few years ago where a few lucky people, like chuckles, got their signature switched with someone else. Every now and then another one from back in the day pops up.