Always Awesome Bar
I personally hate the fact that when you bring up the Add-on Manager, the URL bar goes away. If you're annoyed by that as well, I've created an add-on to solve that - Always Awesome Bar.
With this add-on installed, URLs that typically make the URL bar go away behave like normal URLs.
I get a bit annoyed too, but I content myself with the knowledge that this was done to protect users from being spoofed by websites.
You're mistaken as to what this add-on does. It puts the URL bar back in certain cases. Firefox UI folks made a conscious decision to remove the URL bar in some cases when internal pages are shown. This removes that feature.
Judging by the screenshot, the add-on manager could be spoofed by webpages now.
Chrome doesn't seem to have that problem...
If you can't figure out that it's not the real add-ons page by looking at the URL bar, you probably shouldn't be installing this extension (or any extension for that matter ).
But unfortunately it's not installable here for Seamonkey from Addon wep page. It would be nice to have a link to the xpi file.
Seamonkey doesn't have this problem (at least not from what I see). If you go to about:addons, it still shows the URL bar...