April 17, 2021
https://issues.dlang.org/show_bug.cgi?id=21838

          Issue ID: 21838
           Summary: std.format: Grouping garbles up %a output
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: bugzilla@bernis-buecher.de

assert(format!"%#,a"(0.0) == "0x0.p+0");

--