Great idea and good start Rated 4 out of 5 stars

I'm in exactly that position - something keeps changing my language settings. I've installed this extension and now waiting for it to happen again.

Immediate observations / ideas:
- Ignore certain sources of notifications (the Lastpass extension seems to trigger Type 3 notifications a lot)
- 'More Info' button opens multiple copies of the error console - could it check and just bring the open one to the front?
- The 'cross' icon in the error console makes it look like you can click to clear that message, but it doesn't do anything...
- The error console was (randomly?) cleared, so now I can't see if I missed the change I was looking for - might not be this extension which did that, but if not, need a dedicated logging window rather than relying on Error Console.



This review is for a previous version of the add-on (1.4.1-signed.1-signed). 

PrefMon 1.5 has been released.

- Issues 1-2 should be fixed.

- Issues 3-4 are something of Firefox itself.

Regarding issue 4, the messages on the error console will now get filtered - Usage of the Console2 add-on is highly recommended.

Thanks for your review.