I don't think that IE's behavior is a bug, in fact. IIRC, the W3 spec does not specify the behavior of nested tables. To be honest, I think IE6's behavior makes more sense: tables (and likely other elements, though I have not verified that) inherit attributes from their parents unless otherwise specified.
Also, I doubt it is a bug since the XHTML 1.0 spec was written by members of the W3C HTML working group, which includes at least two people from Microsoft.
"One word of warning: if you meet a bunch of Perl programmers on the bus or something, don't look them in the eye. They've been known to try to convert the young into Perl monks." - Frank Willison