Sorry, I am not using the current versions of Firefox that have that new "push" feature, so my experience with it is limited. I primarily use the ESR version to minimize the number of 'lost' extensions; and "deal with" lost extensions every 7 to 8 versions, instead.

There are a couple of preferences hidden in about:config that may allow you to globally disable that push feature, if you so wish.

dom.push.connection.enabled dom.push.enabled

Try toggling those prefs off and see if that will work to your satisfaction.

As far as a "Never" setting, I'm hoping that some enterprising extension developer comes up with an add-on that allows turning off "push" either per domain or globally, to affect a "Never" setting in a UI.

I really haven't decided if I want to receive pushed notifications or not so blocking all right now is not the right thing to do. I am in a forum at one particular website where the popup appears with almost every mouse click and the options don't include blocking notifications for that site alone.

How about that forum software having an option to turn that feature off? For that forum only ... Check your "Profile" settings for that forum to see if there is a setting for it.

Similar example of forum settings: The forum software used here has a default option for sending an email every time there is a posting made in a forum thread that the user posts in. I didn't realize that when the forum software was changed in 2010, and by the time I realized it I had many thousands of emails from here. An email account that I rarely use.

It appears to me that the forum software is what drives the option offering (popup) for FF. There must be an incompatibility issue there somewhere. I just upgraded to FF 50 hoping that would resolve the issue but it didn't. I know the forum software folks are working on it and they do not have this issue with IE, Chrome and at least one other browser.

Sorry, that's all I got.

Thanks anyway.