It's easy to specify a particular column gap where a column-rule should not appear, or a row gap where a row-rule should not appear. What about specifying a particular column or cell where a row-rule should not appear, or a particular row or cell where a column-rule should not appear? Perhaps a subgrid solution works well enough?

For a very simple "real world" example, I did try using column-rule on my personal site but didn't want them on the first row:

This is somewhat related to the issue about gap decorations in empty grid areas in that both relate to wanting more control over where gap decorations appear.