Having been an apprentice in the trade when these were being installed, I can recall the electricians complaining to the contractor about how junky they were. They proliferated due to low cost - and are no longer used for a reason. Hard to be a Sq D QO that has been around at least since the 70's.
We continually get reports from home buyers that home inspectors have written reports stating the they are not safe. In all honesty, I have blown apart some nice Kliens without the breakers tripping and have seen them burned up in panels.
As far as replacing them, I tell customer that they were never the best quality panels and I'd recommend replacing it if they're concerned, but it's not required.
As far as them not tripping in Canada...
