The table that the badges interface uses, which it gives the class "collection" overrides the default generaltable class.

Most (though not all) other uses seem to pass this class in as well as the actual classname for the table:

git grep table..attributes..class

If it did then it would pick up the standard styling and not require to rebuild it's own styles. And many lines of CSS could be deleted, and as a result the table would be easier to theme.

While I'm here there seems to be many lines intended to tweak the table until it displays absolutely perfectly. Simply deleting these doesn't seem to make much difference after the generaltable class is added.

The table.collection seems to be created twice, so it's probably used in two contexts and possibly there's similar issues with table.issuedbadgebox, table.badgeissuedimage, table.badgeissuedinfo which don't sound like tables of data, just going by the CSS for them.