Yes it has, but it doesn't give any message at all when Quick Quoting.
Ddunk, you can select a part of a post and then press the
button to quote only the part you had selected in Firefox. Need to know for sure you weren't talking about Quick
Reply.
I had this problem for quite a while, that is before and after uninstalling/reinstalling Firefox. But never cleared my profile folder though, because i don't want to loose my extensions. However, a extension could be the cause if other Firefox users don't have this problem.
Could try some more testing tomorrow at a VMware system, but to late for that now.