Arf, I missed that when I searched for ``++NaN++`` in RSPEC... Thanks for noticing it [~ann.campbell.2]. It's indeed a duplicate, but to me RSPEC-2688 is not that good as an explanation. What do you mean by making it a subtask? replacing the existing subtask?
\[~michael.gumowski] the main task talks about using a ``++NaN++``-testing function, which is what this rule also talks about. So yes, replacing the subtask makes sense to me, particularly if you don't like the suggested remediation in the existing subtask.