I'm seeing the same problem with the tables in The Index of the Giant's Comments, and the last post changes were over a week and a half ago. Like Porthos indicated, using a single table CSS class works fine; and like zimmerwald1915 is showing, attempting a combination of table classes results in the default table formatting.

My offhand/uninformed guess is that for whatever reason, the style parsing is trying to read the space-separated lists of CSS class names as a single class name, and since there isn't an exact match for that name no CSS class is applied.