Negative top margin on cleared element following a float with negative top margin

Opera 9-10 seems to get this wrong!   Is this a bug or just a browser inconsistency?

Reported Opera bug DSK-272679
Dec. 1, 2009 - Ray H.

div.static (height:350px)

See This Test Case for the conditions which cause the cleared div to remain blocked by the float in Opera.

All browsers give slightly varied results when the float's negative top margin is Larger than it's Height. Opera is the only one that lets the cleared div escape when a negative top margin on the float is equal to or greater than the floats height.

div.float
(height:100px; margin-top:-100px)

Opera allows the cleared div to escape the float since
the floats negative margin is equal to it's height.

In flow div.clear
(margin-top:-400px)