Starting with version 40, Firefox gives a warning on unsigned (by Mozilla) extensions, while starting with version 41 these extensions won't be allowed to install. There is no option in about:config or similar to disable this behaviour. People not wanting to have this behaviour would need to switch to the Dev-edition (which brings a lot of bloat) or use an unbranded build. As such, the given setting will probably be a compile-time flag for which I'd like to request a USE-flag. Ideally, default state should be signing enabled with a one-time einfo telling people about it. Reproducible: Always
As a heads up, this will not be made mandatory per current plans until firefox-44. Additionally, Firefox ESR 45 will not enforce the mandatory extension signing. See https://wiki.mozilla.org/Add-ons/Extension_Signing for more details.
If you feel I have closed your bug and it is still a current issue, please reopen and update it completely. We will not work bugs that have no ebuild in tree any longer or can not be reproduced with a current system. Thank You for your support and understanding The Mozilla Team
