The two blocks should be identical, including overflow.
IE8 Mode and IE9 Mode (All Versions)
The two blocks are not identical because there is no space between "lll" and "mmm" in the last span element of the second block.
The test fails because Unicode 'RIGHT-TO-LEFT-OVERRIDE' (U+202E) character changes the position of surrounding white space, thus affecting white-space collapsing.
Section 2.1.83, V0499