Is it unusual for a dissenting Supreme Court justice not to write a separate opinion?
In 40 out of 63 opinions in Supreme Court cases in 2019, at least one of the nine justices disagreed with the majority decision. In most cases that aren't unanimous, the court typically publishes a dissent written by a justice, explaining the reasons for the disagreement. Others may join in signing that dissent, or, on occasion, provide their own.
In one case in the last term, Sharp v. Murphy, no dissent was published. The court simply noted the dissent by two justices. In both decisions published so far in the current term, the court, similarly, noted the dissent of Justice Clarence Thomas in each case.
Justices also occasionally write opinions to accompany various orders preceding consideration of a final case, such as upholding or rejecting a lower court ruling in an ongoing case. More often, no explanation is offered.