We have received multiple reports asking for the ability for form authors to delete some or all responses submitted to a form. One often cited use case is when the author wants to test their form but then exclude their test from the responses once the form is live.
We had initially ruled out this option as it opens up some problematic cases. For example if there are multiple authors on a form used for voting, one could use this feature to manipulate the results.
However due to this feature being requested multiple times we are considering if and how to implement it.
Source: multiple support tickets and chat questions