'border-style' values of column-rule are interpreted as in the collapsing border model in which case 'inset' value is drawn the same as 'ridge'. This bug was found by the test: LayoutTests/imported/w3c/css/css-multicol-1/multicol-rule-inset-000.xht. which was written by Håkon Wium Lie who was the author of the multicolumn layout mode spec.
<rdar://problem/22582086>
multicol-rule-outset-000.xht also fails: 'border-style' values of column-rule are interpreted as in the collapsing border model in which case 'outset' value is drawn the same as 'groove'.
*** This bug has been marked as a duplicate of bug 148815 ***