I added some traces in Tear event handlers.
It seems tso was right.
When I press the "back" button (short press), sometimes tear receives a key_down event, and then about a second later, a delete event (which causes the current window to close), and then a key_up event.
So it looks like a problem outside Tear (but i've never noticed it with any other application).

As I'm the only one with this problem, i'll just patch my copy of tear to disable window closing on "back" long press and won't bother you again with this

btw Bundyo, it would be nice to publish up to date webkit dev package in some repository to enable people to easily hack with tear code