Consider the following exchange:
They were sitting on the bench.
The dialogue lines are indented. Should the descriptive sentence also be indented? What if we had
They were sitting on the bench, feet naked against the ground, blah blah blah blah blah blah **new line*
Since this is a full paragraph, should it be indented? (My gut thinks yes). If so, would we then indent the firsts sentence as well?