Currently, the "Version" field of our bugs can only be set to one of "compat (1.0)", "core (2.0)" or "unspecified". Why not to create a new "both" option to explicitly indicate that the bug is valid for both versions? So, "unspecified" would only mean that the bug has not been tested on both versions. (Ideally, the "version" field should consist of two checkboxes, one for each version.)