Created attachment 115362 [details]
Fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=1209753#c25 has a recording of palm events, some of which are in the top area but outside of the palm detection edges. In that particular recording the events are at roughly 22% of the touchpad width (no abs measurement available)
Maybe we should consider a top area similar to the edges atm, with the same behaviour. This area isn't needed on the T440s since they already ignore events in that area due to the top software buttons.
giving up on that idea, the few recordings with top palm events I've seen so far had nothing much in common, and it's quite laptop-dependent anyway.