I’m not crazy! At least not yet… In that way… 
The reference was actually in that old forum : https://groups.google.com/forum/#!topic/qubes-users/oStl_IGHuLQ
I took a look at the referenced Mozilla bug and it’s still open, so presumably this is still a concern? Not sure if the listed mitigations are (still?) the appropriate ones to take…
Appreciate any thoughts you, and others, have!
(And given the direction this thread took, you may wish to split this out?)