Why was the Supreme Court's decision in RNC v. DNC unsigned?

Because applications for stay decided without oral argument are (in my experience) always unsigned, per curiam decisions.

Linda Greenhouse's column criticizes the Supreme Court's recent order in RNC v. DNC, which considered absentee ballots in Wisconsin. She criticizes the majority for issuing an unsigned, per curiam decision.

I wonder how Chief Justice John Roberts and Justices Clarence Thomas, Samuel Alito, Neil Gorsuch and Brett Kavanaugh understand the word "ordinarily." And I wonder why the opinion was issued per curiam — "by the court." Did none of the five have the nerve to take ownership by signing his name?

In contrast, Greenhouse notes, the dissenters signed their opinion:

The other three dissenting justices all signed Justice Ginsburg's opinion; she spoke for them all.

The Court's common practice is to issue unsigned, per curiam opinions in response to stay applications that are resolved without oral arguments. There may be exceptions. I welcome any tips from Greenhouse, who has studied the Court far longer than I have, or anyone else. But I can't think of any off the top of my head. In contrast, dissents from per curiam decisions are always signed. I have never seen a per curiam dissent.

Indeed, we cannot presume that a Justice joins a per curiam decision on a stay application, simply because he or she does not dissent. Several of the Justices have reiterated this point over the years. We can only figure out the vote count in such a per curiam case where there are four dissenters; then we know who the five members were that constituted a majority.

There is nothing to "wonder" about here. There are no questions of "nerve." We are dealing here with the Court's standard operating procedures.