Originally Posted by Beorn
Well then, it really seems quite strange that for you it doesn't happen...
I would wager that this is because "not all 'mock' SD cards are created equal". I would be surprised to learn that there is a formal specification for the manufacturing of this placeholder cards.
I've never heard of SD slots using a mechanical switch to detect a card insert, I've always assumed it was an electrical signal accomplished via the SD card contacts completing a circuit on the device (those familiar with electronics know what I mean).
So if the mock card you have was made for a slot that doesn't have this weird switch the Kobo uses to detect an insert, it wouldn't be designed to avoid hitting that switch.